Dual interpretation of a length field of a signal unit

ABSTRACT

A method includes generating, at a second wireless device, a signal (SIG) unit to be transmitted to a first wireless device. The SIG unit includes a length field and an aggregation field. In response to determining to use aggregated transmission to the first wireless device, the method further includes setting the aggregation field to a first value and setting the length field to a number of symbols. In response to determining not to use the aggregated transmission to the first wireless device, the method further includes setting the aggregation field to a second value and setting the length field to a number of bytes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of, and claimspriority to, U.S. patent application Ser. No. 13/604,030 filed Sep. 5,2012, which claims priority from the following commonly owned U.S.Provisional Patent Applications, the contents of which are expresslyincorporated herein by reference in their entirety: No. 61/531,584 filedSep. 6, 2011, No. 61/562,063 filed Nov. 21, 2011, No. 61/564,177 filedNov. 28, 2011, No. 61/566,961 field Dec. 5, 2011, No. 61/580,616 filedDec. 27, 2011, No. 61/585,479 filed Jan. 11, 2012, No. 61/585,573 filedJan. 11, 2012, No. 61/670,092 filed Jul. 10, 2012, and No. 61/684,248filed Aug. 17, 2012.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to wireless communications, andmore specifically to SIGNAL (SIG) units communicated via wirelessnetworks.

BACKGROUND

In many telecommunication systems, communications networks are used toexchange messages among several interacting spatially-separated devices.Networks may be classified according to geographic scope, which couldbe, for example, a wide area, a metropolitan area, a local area, or apersonal area. Such networks would be designated respectively as a widearea network (WAN), metropolitan area network (MAN), local area network(LAN), or personal area network (PAN). Networks also differ according tothe switching/routing technique used to interconnect the various networknodes and devices (e.g. circuit switching vs. packet switching), thetype of physical media employed for transmission (e.g. wired vs.wireless), and the set of communication protocols used (e.g. Internetprotocol suite, SONET (Synchronous Optical Networking), Ethernet, etc.).

Wireless networks are often preferred when the network elements aremobile and thus have dynamic connectivity needs, or if the networkarchitecture is formed in an ad hoc, rather than fixed, topology.Wireless networks employ intangible physical media in an unguidedpropagation mode using electromagnetic waves in the radio, microwave,infra-red, optical, etc. frequency bands. Wireless networksadvantageously facilitate user mobility and rapid field deployment whencompared to fixed wired networks.

The devices in a wireless network may transmit/receive informationbetween each other. The information may include packets, which in someaspects may be referred to as data units. The packets may includeoverhead information (e.g., header information, packet properties, etc.)that helps in routing the packet through the network, identifying thedata in the packet, processing the packet, etc., as well as data, forexample user data, multimedia content, etc. as might be carried in apayload of the packet.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include decreasingthe overhead in transmitting payloads in data packets.

In a particular embodiment, a method includes receiving, at a firstwireless device from a second wireless device, a signal (SIG) unitincluding a length field and an aggregation field. The method alsoincludes interpreting the length field as a number of symbols inresponse to determining that the aggregation field has a first value andinterpreting the length field as a number of bytes in response todetermining that the aggregation field has a second value.

In another particular embodiment, a method includes generating, at asecond wireless device, a SIG unit to be transmitted to a first wirelessdevice, where the SIG unit includes a length field and an aggregationfield. The method also includes, in response to determining to useaggregated transmission to the first wireless device, setting theaggregation field to a first value and setting the length field to anumber of symbols. The method further includes, in response todetermining not to use the aggregated transmission to the first wirelessdevice, setting the aggregation field to a second value and setting thelength field to a number of bytes.

In another particular embodiment, a method includes receiving, at awireless device, a frame via a sub-1 gigahertz (GHz) wireless network.The frame includes a SIG unit having a length field and an aggregationfield. The method also includes, in response to determining that theframe is associated with a 1 megahertz (MHz) bandwidth mode,interpreting the length field as a number of bytes or a number ofsymbols based on a value of the aggregation field. The method furtherincludes, in response to determining that the frame is not associatedwith the 1 MHz bandwidth mode, determining whether the frame includes ashort format preamble or a long format preamble. The method includes, inresponse to determining that the frame includes the short formatpreamble, interpreting the length field as a number of bytes or a numberof symbols based on the value of the aggregation field. The method alsoincludes, in response to determining that the frame includes the longformat preamble, determining whether the frame is a single user (SU)frame or a multi user (MU) frame. The method further includes, inresponse to determining that the frame is the SU frame, interpreting thelength field as a number of bytes or a number of symbols based on thevalue of the aggregation field. The method includes, in response todetermining that the frame is the MU frame, interpreting the lengthfield as a number of symbols.

In another particular embodiment, an apparatus includes a receiverconfigured to receive a SIG unit having a length field and anaggregation field. The apparatus also includes a processor configured tointerpret the length field as a number of symbols in response todetermining that the aggregation field has a first value and tointerpret the length field as a number of bytes in response todetermining that the aggregation field has a second value.

In another particular embodiment, an apparatus includes a processorconfigured to generate a SIG unit having a length field and anaggregation field. The processor is also configured to, in response todetermining to use aggregated transmission, set the aggregation field toa first value and set the length field to a number of symbols. Theprocessor is further configured to in response to determining not to usethe aggregated transmission, set the aggregation field to a second valueand set the length field to a number of bytes. The apparatus alsoincludes a transmitter configured to transmit the SIG unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless communication system inwhich aspects of the present disclosure may be employed.

FIG. 2 shows a functional block diagram of an exemplary wireless devicethat may be employed within the wireless communication system of FIG. 1.

FIG. 3 shows a functional block diagram of exemplary components that maybe utilized in the wireless device of FIG. 2 to transmit wirelesscommunications.

FIG. 4 shows a functional block diagram of exemplary components that maybe utilized in the wireless device of FIG. 2 to receive wirelesscommunications.

FIG. 5 illustrates an example of a physical layer data unit.

FIG. 6 shows a flow chart of an aspect of an exemplary method forgenerating and transmitting a data unit.

FIG. 7 shows a flow chart of another aspect of an exemplary method forreceiving and processing a data unit including a signal unit.

FIG. 8 shows a flow chart of another aspect of an exemplary method forgenerating and transmitting a data unit.

FIG. 9 shows a flow chart of another aspect of an exemplary method forreceiving and processing a data unit including a signal unit.

FIG. 10 is a functional block diagram of another exemplary wirelessdevice that may be employed within the wireless communication system ofFIG. 1.

FIG. 11 is a functional block diagram of yet another exemplary wirelessdevice that may be employed within the wireless communication system ofFIG. 1.

DETAILED DESCRIPTION

Various aspects of the systems, apparatuses, and methods are describedmore fully hereinafter with reference to the accompanying drawings. Theteachings of the disclosure may, however, be embodied in many differentforms and should not be construed as limited to any specific structureor function presented throughout this disclosure. Rather, these aspectsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the disclosure to those skilled in theart. Based on the teachings herein one skilled in the art shouldappreciate that the scope of the disclosure is intended to cover anyaspect of the novel systems, apparatuses, and methods disclosed herein,whether implemented independently of or combined with any other aspectof the disclosure. For example, an apparatus may be implemented or amethod may be practiced using any number of the aspects set forthherein. In addition, the scope of the disclosure is intended to coversuch an apparatus or method which is practiced using other structure,functionality, or structure and functionality in addition to or otherthan the various aspects of the disclosure set forth herein. It shouldbe understood that any aspect disclosed herein may be embodied by one ormore elements of a claim.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of particular aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description. The detailed description anddrawings are merely illustrative of the disclosure rather than limiting,the scope of the disclosure being defined by the appended claims andequivalents thereof.

Wireless network technologies may include various types of wirelesslocal area networks (WLANs). A WLAN may be used to interconnect nearbydevices together, employing widely used networking protocols. Thevarious aspects described herein may apply to any communicationstandard, such as WiFi or, more generally, any member of the IEEE 802.11family of wireless protocols. For example, the various aspects describedherein may be used as part of the IEEE 802.11ah protocol, which usessub-1 GHz bands.

In some aspects, wireless signals in a sub-gigahertz band may betransmitted according to the 802.11ah protocol using orthogonalfrequency-division multiplexing (OFDM), direct-sequence spread spectrum(DSSS) communications, a combination of OFDM and DSSS communications, orother schemes. Implementations of the 802.11ah protocol may be used forsensors, metering, and smart grid networks. Advantageously, aspects ofcertain devices implementing the 802.11ah protocol may consume lesspower than devices implementing other wireless protocols, and/or may beused to transmit wireless signals across a relatively long range, forexample about one kilometer or longer.

In some implementations, a WLAN includes various devices which are thecomponents that access the wireless network. For example, there may betwo types of devices: access points (“APs”) and clients (also referredto as stations, or “STAs”). In general, an AP serves as a hub or basestation for the WLAN, and an STA serves as a user of the WLAN. Forexample, an STA may be a laptop computer, a personal digital assistant(PDA), a mobile phone, etc. In an example, an STA connects to an AP viaa WiFi (e.g., IEEE 802.11 protocol such as 802.11ah) compliant wirelesslink to obtain general connectivity to the Internet or to other widearea networks. In some implementations an STA may also be used as an AP.

An access point (“AP”) may also include, be implemented as, or known asa NodeB, Radio Network Controller (“RNC”), eNodeB, Base StationController (“BSC”), Base Transceiver Station (“BTS”), Base Station(“BS”), Transceiver Function (“TF”), Radio Router, Radio Transceiver, orsome other terminology.

A station (“STA”) may also include, be implemented as, or known as anaccess terminal (“AT”), a subscriber station, a subscriber unit, amobile station, a remote station, a remote terminal, a user terminal, auser agent, a user device, user equipment, or some other terminology. Insome implementations an access terminal may include a cellulartelephone, a cordless telephone, a Session Initiation Protocol (“SIP”)phone, a wireless local loop (“WLL”) station, a personal digitalassistant (“PDA”), a handheld device having wireless connectioncapability, or some other suitable processing device connected to awireless modem. Accordingly, one or more aspects taught herein may beincorporated into a phone (e.g., a cellular phone or smartphone), acomputer (e.g., a laptop), a portable communication device, a headset, aportable computing device (e.g., a personal data assistant), anentertainment device (e.g., a music or video device, or a satelliteradio), a gaming device or system, a global positioning system device,or any other suitable device that is configured to communicate via awireless medium.

As discussed above, certain of the devices described herein mayimplement the 802.11ah standard, for example. Such devices, whether usedas an STA or AP or other device, may be used for smart metering or in asmart grid network. Such devices may provide sensor applications or beused in home automation. The devices may instead or in addition be usedin a healthcare context, for example for personal healthcare. They mayalso be used for surveillance, to enable extended-range Internetconnectivity (e.g. for use with hotspots), or to implementmachine-to-machine communications.

FIG. 1 illustrates an example of a wireless communication system 100 inwhich aspects of the present disclosure may be employed. The wirelesscommunication system 100 may operate pursuant to a wireless standard,for example the 802.11ah standard. The wireless communication system 100may include an AP 104, which communicates with STAs 106.

A variety of processes and methods may be used for transmissions in thewireless communication system 100 between the AP 104 and the STAs 106.For example, signals may be sent and received between the AP 104 and theSTAs 106 in accordance with OFDM/OFDMA techniques. If this is the case,the wireless communication system 100 may be referred to as anOFDM/OFDMA system. Alternatively, signals may be sent and receivedbetween the AP 104 and the STAs 106 in accordance with CDMA techniques.If this is the case, the wireless communication system 100 may bereferred to as a CDMA system.

A communication link that facilitates transmission from the AP 104 toone or more of the STAs 106 may be referred to as a downlink (DL) 108,and a communication link that facilitates transmission from one or moreof the STAs 106 to the AP 104 may be referred to as an uplink (UL) 110.Alternatively, a downlink 108 may be referred to as a forward link or aforward channel, and an uplink 110 may be referred to as a reverse linkor a reverse channel.

The AP 104 may act as a base station and provide wireless communicationcoverage in a basic service area (BSA) 102. The AP 104 along with theSTAs 106 associated with the AP 104 and that use the AP 104 forcommunication may be referred to as a basic service set (BSS). It shouldbe noted that the wireless communication system 100 may not have acentral AP 104, but rather may function as a peer-to-peer networkbetween the STAs 106. Accordingly, the functions of the AP 104 describedherein may alternatively be performed by one or more of the STAs 106.

As further described herein, packets (e.g., illustrative packet 140)(alternately referred to herein as data units or frames) transmittedbetween the AP 104 and the STAs 106 may include a SIGNAL (SIG) unit(alternately referred to herein as a SIG field). For example, the SIGunit may be included in a physical layer (PHY) preamble of a packet. TheSIG unit may include control information that can be used to decode thepacket or a data payload thereof. In a particular embodiment, a lengthfield of the SIG unit may indicate a length of the packet or datapayload thereof. The length field may have a fixed size, such as ninebits. However, the unit of measurement represented by the length fieldmay vary. For example, when data aggregation is not in use (e.g.,indicated by an aggregation field of the SIG unit having a first value),the length field may represent a number of bytes. Since 2=512, the SIGunit may be able to indicate packet sizes ranging from 0 to 511 bytes.When data aggregation is in use (e.g., indicated by the aggregationfield of the SIG unit having a second value), the length field mayrepresent a number of symbols and may thus be able to represent sizeslarger than 511 bytes.

In a particular embodiment, as further described herein, one or morefields of a SIG unit may support the use of “exceptional” values toindicate alternative data formats, payload lengths, and types. Forexample, a particular value of a particular field of the SIG unit mayindicate that another field of the SIG unit is to be interpretedunconventionally, that the SIG unit is part of a packet that has azero-length payload, or that the SIG unit is part of a particular typeof packet. For example, a particular value of a modulation and codingscheme (MCS) field may indicate that the SIG unit is part of anacknowledgement (ACK) packet that has a zero-length payload (e.g., anACK packet that is represented entirely by PHY data).

FIG. 2 illustrates various components that may be utilized in a wirelessdevice 202 that may be employed within the wireless communication system100. The wireless device 202 is an example of a device that may beconfigured to implement the various methods described herein. Forexample, the wireless device 202 may include the AP 104 or one of theSTAs 106.

The wireless device 202 may include a processor 204 which controlsoperation of the wireless device 202. The processor 204 may also bereferred to as a central processing unit (CPU). Memory 206, which mayinclude both read-only memory (ROM) and random access memory (RAM),provides instructions and data to the processor 204. A portion of thememory 206 may also include non-volatile random access memory (NVRAM).The processor 204 typically performs logical and arithmetic operationsbased on program instructions stored within the memory 206. Theinstructions in the memory 206 may be executable to implement themethods described herein.

The processor 204 may include or be a component of a processing systemimplemented with one or more processors. The one or more processors maybe implemented with any combination of general-purpose microprocessors,microcontrollers, digital signal processors (DSPs), field programmablegate array (FPGAs), programmable logic devices (PLDs), controllers,state machines, gated logic, discrete hardware components, dedicatedhardware finite state machines, or any other suitable entities that canperform calculations or other manipulations of information.

The processing system may also include machine-readable media forstoring software. Software shall be construed broadly to mean any typeof instructions, whether referred to as software, firmware, middleware,microcode, hardware description language, or otherwise. Instructions mayinclude code (e.g., in source code format, binary code format,executable code format, or any other suitable format of code). Theinstructions, when executed by the one or more processors, cause theprocessing system to perform the various functions described herein.

The wireless device 202 may also include a housing 208 that may includea transmitter 210 and a receiver 212 to allow transmission and receptionof data between the wireless device 202 and a remote location. Thetransmitter 210 and receiver 212 may be combined into a transceiver 214.An antenna 216 may be attached to the housing 208 and electricallycoupled to the transceiver 214. The wireless device 202 may also include(not shown) multiple transmitters, multiple receivers, multipletransceivers, and/or multiple antennas. As further described herein, thetransmitter 210 may be means for transmitting a SIG unit and thereceiver 212 may be means for receiving a SIG unit.

The wireless device 202 may also include a signal detector 218 that maybe used in an effort to detect and quantify the level of signalsreceived by the transceiver 214. The signal detector 218 may detectcharacteristics of signals, such as total energy, energy per subcarrierper symbol, and power spectral density. The wireless device 202 may alsoinclude a digital signal processor (DSP) 220 for use in processingsignals. The DSP 220 may be configured to generate a data unit fortransmission. In some aspects, the data unit may include a physicallayer data unit (PPDU). In some aspects, the PPDU is referred to as apacket. As further described herein, one or more of the processor 204,the signal detector 218, and the DSP 220 may be means for generating aSIG unit, means for interpreting a length field of a SIG unit, means fordetermining whether a field of the SIG unit has a value indicating azero-length payload, and/or means for decoding the SIG unit based on thedetermination.

The wireless device 202 may further include a user interface 222 in someaspects. The user interface 222 may include a keypad, a microphone, aspeaker, and/or a display. The user interface 222 may include anyelement or component that conveys information to a user of the wirelessdevice 202 and/or receives input from the user.

The various components of the wireless device 202 may be coupledtogether by a bus system 226. The bus system 226 may include a data bus,for example, as well as a power bus, a control signal bus, and a statussignal bus in addition to the data bus. Those of skill in the art willappreciate the components of the wireless device 202 may be coupledtogether or accept or provide inputs to each other using some othermechanism.

Although a number of separate components are illustrated in FIG. 2,those of skill in the art will recognize that one or more of thecomponents may be combined or commonly implemented. For example, theprocessor 204 may be used to implement not only the functionalitydescribed above with respect to the processor 204, but also to implementthe functionality described above with respect to the signal detector218 and/or the DSP 220. Further, each of the components illustrated inFIG. 2 may be implemented using a plurality of separate elements.

As discussed above, the wireless device 202 may include an AP 104 or anSTA 106, and may be used to transmit and/or receive communications. Forexample, the wireless device 202 may communicate a packet 240 thatincludes a SIG unit. As further described herein, the packet 240 mayinclude a SIG unit having a length field that can be interpreted inmultiple ways based on the value of another field in the SIG unit. Forexample, the length field may be interpreted as a number of bytes or anumber of symbols based on the value of an aggregation field.Alternately, or in addition, the presence of a particular value in aparticular field of the SIG unit may indicate that the packet 240 has azero-length payload (e.g., is a short ACK that is entirely representedby PHY data).

FIG. 3 illustrates various components that may be utilized in thewireless device 202 to transmit wireless communications. The componentsillustrated in FIG. 3 may be used, for example, to transmit OFDMcommunications. In some aspects, the components illustrated in FIG. 3are used to transmit data units with SIGNAL units (e.g., the packet 240of FIG. 2) in various communication modes, as will be discussed inadditional detail below. For ease of reference, the wireless device 202configured with the components illustrated in FIG. 3 is hereinafterreferred to as a wireless device 202 a.

The wireless device 202 a may include a modulator 302 configured tomodulate bits for transmission. For example, the modulator 302 maydetermine a plurality of symbols from bits received from the processor204 or the user interface 222, for example by mapping bits to aplurality of symbols according to a constellation. The bits maycorrespond to user data or to control information. In some aspects, thebits are received in codewords. In one aspect, the modulator 302includes a QAM (quadrature amplitude modulation) modulator, for examplea 16-QAM modulator or a 64-QAM modulator. In other aspects, themodulator 302 includes a binary phase-shift keying (BPSK) modulator or aquadrature phase-shift keying (QPSK) modulator.

The wireless device 202 a may further include a transform module 304configured to convert symbols or otherwise modulated bits from themodulator 302 into a time domain. In FIG. 3, the transform module 304 isillustrated as being implemented by an inverse fast Fourier transform(IFFT) module. In some implementations, there may be multiple transformmodules (not shown) that transform units of data of different sizes.

In FIG. 3, the modulator 302 and the transform module 304 areillustrated as being implemented in the DSP 220. In some aspects,however, one or both of the modulator 302 and the transform module 304are implemented in the processor 204 or in another element of thewireless device 202.

As discussed above, the DSP 220 may be configured to generate a dataunit for transmission. In some aspects, the modulator 302 and thetransform module 304 may be configured to generate a data unit includinga plurality of fields including control information and a plurality ofdata symbols. The fields including the control information may includeone or more training fields, for example, and one or more signal (SIG)fields. Each of the training fields may include a known sequence of bitsor symbols. Each of the SIG fields may include information about thedata unit, for example a description of a length or data rate of thedata unit.

Returning to the description of FIG. 3, the wireless device 202 a mayfurther include a digital to analog converter (DAC, designated “D/A” inFIG. 3) 306 configured to convert the output of the transform moduleinto an analog signal. For example, the time-domain output of thetransform module 304 may be converted to a baseband OFDM signal by thedigital to analog converter 306. The digital to analog converter 306 maybe implemented in the processor 204 or in another element of thewireless device 202. In some aspects, the digital to analog converter306 is implemented in the transceiver 214 or in a data transmitprocessor.

The analog signal may be wirelessly transmitted by the transmitter 210.The analog signal may be further processed before being transmitted bythe transmitter 210, for example by being filtered or by beingupconverted to an intermediate or carrier frequency. In the aspectillustrated in FIG. 3, the transmitter 210 includes a transmit amplifier308. Prior to being transmitted, the analog signal may be amplified bythe transmit amplifier 308. In some aspects, the amplifier 308 includesa low noise amplifier (LNA).

The transmitter 210 is configured to transmit one or more packets ordata units in a wireless signal based on the analog signal. The dataunits may be generated using the processor 204 and/or the DSP 220, forexample using the modulator 302 and the transform module 304 asdiscussed above. Data units that may be generated and transmitted asdiscussed above are described in additional detail below with respect toFIGS. 5-11.

FIG. 4 illustrates various components that may be utilized in thewireless device 202 to receive wireless communications. The componentsillustrated in FIG. 4 may be used, for example, to receive OFDMcommunications. In some aspects, the components illustrated in FIG. 4are used to receive data units that include one or more SIGNAL units(e.g., the packet 240 of FIG. 2), as will be discussed in additionaldetail below. For example, the components illustrated in FIG. 4 may beused to receive data units transmitted by the components discussed abovewith respect to FIG. 3. For ease of reference, the wireless device 202configured with the components illustrated in FIG. 4 is hereinafterreferred to as a wireless device 202 b.

The receiver 212 is configured to receive one or more packets or dataunits in a wireless signal. Data units that may be received and decodedor otherwise processed as discussed below are described in additionaldetail with respect to FIGS. 5-11.

In the aspect illustrated in FIG. 4, the receiver 212 includes a receiveamplifier 401. The receive amplifier 401 may be configured to amplifythe wireless signal received by the receiver 212. In some aspects, thereceiver 212 is configured to adjust the gain of the receive amplifier401 using an automatic gain control (AGC) procedure. In some aspects,the automatic gain control uses information in one or more receivedtraining fields, such as a received short training field (STF) forexample, to adjust the gain. Those having ordinary skill in the art willunderstand methods for performing AGC. In some aspects, the amplifier401 includes a LNA.

The wireless device 202 b may include an analog to digital converter(ADC, designated “A/D” in FIG. 4) 402 configured to convert theamplified wireless signal from the receiver 212 into a digitalrepresentation thereof. Further to being amplified, the wireless signalmay be processed before being converted by the analog to digitalconverter 402, for example by being filtered or by being downconvertedto an intermediate or baseband frequency. The analog to digitalconverter 402 may be implemented in the processor 204 or in anotherelement of the wireless device 202. In some aspects, the analog todigital converter 402 is implemented in the transceiver 214 or in a datareceive processor.

The wireless device 202 b may further include a transform module 404configured to convert the representation the wireless signal into afrequency spectrum. In FIG. 4, the transform module 404 is illustratedas being implemented by a fast Fourier transform (FFT) module. Thetransform module 404 may be programmable, and may be configured toperform FFT with different configurations. In one aspect, for example,the transform module 404 may be configured to perform either a 32-pointFFT or a 64-point FFT. In some aspects, the transform module 404 mayidentify a symbol for each point that it uses.

The wireless device 202 b may further include a channel estimator andequalizer 405 configured to form an estimate of the channel over whichthe data unit is received, and to remove certain effects of the channelbased on the channel estimate. For example, the channel estimator may beconfigured to approximate a function of the channel, and the channelequalizer may be configured to apply an inverse of that function to thedata in the frequency spectrum.

In some aspects, the channel estimator and equalizer 405 usesinformation in one or more received training fields, such as a longtraining field (LTF) for example, to estimate the channel. The channelestimate may be formed based on one or more LTFs received at thebeginning of the data unit. This channel estimate may thereafter be usedto equalize data symbols that follow the one or more LTFs. After acertain period of time or after a certain number of data symbols, one ormore additional LTFs may be received in the data unit. The channelestimate may be updated or a new estimate formed using the additionalLTFs. This new or update channel estimate may be used to equalize datasymbols that follow the additional LTFs. In some aspects, the new orupdated channel estimate is used to re-equalize data symbols precedingthe additional LTFs. Those having ordinary skill in the art willunderstand methods for forming a channel estimate.

The wireless device 202 b may further include a demodulator 406configured to demodulate the equalized data. For example, thedemodulator 406 may determine a plurality of bits from symbols output bythe transform module 404 and the channel estimator and equalizer 405,for example by reversing a mapping of bits to a symbol in aconstellation. The bits may be processed or evaluated by the processor204, or used to display or otherwise output information to the userinterface 222. In this way, data and/or information may be decoded. Insome aspects, the bits correspond to codewords. In one aspect, thedemodulator 406 includes a QAM (quadrature amplitude modulation)demodulator, for example a 16-QAM demodulator or a 64-QAM demodulator.In other aspects, the demodulator 406 includes a binary phase-shiftkeying (BPSK) demodulator or a quadrature phase-shift keying (QPSK)demodulator.

In FIG. 4, the transform module 404, the channel estimator and equalizer405, and the demodulator 406 are illustrated as being implemented in theDSP 220. In some aspects, however, one or more of the transform module404, the channel estimator and equalizer 405, and the demodulator 406are implemented in the processor 204 or in another element of thewireless device 202.

As discussed above, the wireless signal received at the receiver 212includes one or more data units. Using the functions or componentsdescribed above, the data units or data symbols therein may be decodedevaluated or otherwise evaluated or processed. For example, theprocessor 204 and/or the DSP 220 may be used to decode data symbols inthe data units using the transform module 404, the channel estimator andequalizer 405, and the demodulator 406.

Data units exchanged by the AP 104 and the STA 106 may include controlinformation or data, as discussed above. At the physical (PHY) layer,these data units may be referred to as physical layer protocol dataunits (PPDUs). In some aspects, a PPDU may be referred to as a packet orphysical layer packet. Each PPDU may include a preamble and a payload.The preamble may include training fields and a SIG field. The payloadmay include a Media Access Control (MAC) header or data for otherlayers, and/or user data, for example. In various embodiments, dataunits can include Mac Protocol Data Units (MPDU) and/or Aggregated MacProtocol Data Units (A-MPDU). The payload may be transmitted using oneor more data symbols. The systems, methods, and devices herein mayutilize data units with training fields whose peak-to-power ratio hasbeen minimized.

The data units may be transmitted, for example, in a 1 MHz mode or a 2MHz mode. The preamble may be common for a 1 MHz normal mode and for a 1MHz 2x repetition mode. In a 2 MHz mode, the SIG field may span 52 datatones. In some embodiments, a SIG field may be replicated every 2 MHzfor transmissions greater than 2 MHz. In addition, for transmissiongreater than 2 MHz, there may be 2 SIG-A fields and 1 SIG-B field for MUmode. In some embodiments, in a 1 MHz mode there may be 6 SIG A fields.In a 1 MHz mode, the SIG field may span 24 data tones. In someembodiments, the 2 MHz PHY transmission is an OFDM based waveformconsisting of 64 tones (52 data tones, 4 pilot tones, 7 guard tones, and1 DC tone). The tone spacing for other bandwidth modes may be the sameas the tone spacing for a 2 MHz mode. In some embodiments, a 1 MHz modeincludes 32 tones (24 data tones, 2 pilot tones, 5 guard tones, and 1 DCtone).

FIG. 5 illustrates an example of a data unit 500. The data unit 500 mayinclude a PPDU for use with the wireless device 202. In an embodiment,the data unit 500 may be used by legacy devices or devices implementinga legacy standard or downclocked version thereof.

The data unit 500 includes a preamble 510. The preamble 510 may includea variable number of repeating STF 512 symbols, and one or more LTF 514symbols. In one implementation 10 repeated STF 512 symbols may be sentfollowed by two LTF 512 symbols. The STF 512 may be used by the receiver212 to perform automatic gain control to adjust the gain of the receiveamplifier 401, as discussed above. Furthermore, the STF 512 sequence maybe used by the receiver 212 for packet detection, rough timing, andother settings. The LTF 514 may be used by the channel estimator andequalizer 405 to form an estimate of the channel over which the dataunit 500 is received.

Following the preamble 510 in the data unit 500 is a SIGNAL unit 520.The SIGNAL 520 unit may be represented using OFDM and may includeinformation relating to the transmission rate, the length of the dataunit 500, and the like. The data unit 500 additionally includes avariable number of data symbols 530, such as OFDM data symbols. In anembodiment, the preamble 510 can include the SIGNAL unit 520. In anembodiment, one or more of the data symbols 530 can be a payload.

When the data unit 500 is received at the wireless device 202 b, thesize of the data unit 500 including the LTFs 514 may be computed basedon the SIGNAL unit 520, and the STF 512 may be used by the receiver 212to adjust the gain of the receive amplifier 401. Further, a LTF may beused by the channel estimator and equalizer 405 to form an estimate ofthe channel over which the data unit 500 is received. The channelestimate may be used by the DSP 220 to decode the plurality of datasymbols 530 that follow the preamble 510.

The data unit 500 illustrated in FIG. 5 is only an example of a dataunit that may be used in the system 100 and/or with the wireless device202. Those having ordinary skill in the art will appreciate that agreater or fewer number of the STFs 412 or LTFs 514 and/or the datasymbols 530 may be included in the data unit 500. In addition, one ormore symbols or fields may be included in the data unit 500 that are notillustrated in FIG. 5, and one or more of the illustrated fields orsymbols may be omitted.

When using OFDM, a number of orthogonal subcarriers of the frequencyband may be used. The number of subcarriers that are used may depend ona variety of considerations including the available frequency bands foruse, bandwidth and any associated regulatory constraints. The number ofsubcarriers used is correlated to the size of an FFT module as eachmodulated subcarrier is an input to an IFFT module to create the OFDMsignal to be transmitted. As such, in some implementations a larger FFTsize (e.g., 64, 128, 256, or 512) may, corresponding to transmittingdata using more subcarriers, be desired to achieve a larger bandwidth.In other implementations, a smaller FFT size may be used fortransmitting data in a narrow bandwidth. The number of subcarriers, andtherefore FFT size, may be chosen so as to comply with regulatorydomains with certain bandwidth restrictions. For example, an FFT size of32 may be provided for certain implementations (e.g., for down clockedimplementations), and provided for use for 802.11ah. As such, thewireless device 202 a may include several transform modules 304, eachimplemented as an FFT or IFFT module, each of a different size so as tocomply with the number of subcarriers specified to be used. At least oneof the transform modules 304 may be a 32-point size IFFT or FFT moduleaccording to certain aspects described herein. In an embodiment, thetransform module 304 may be configured to selectively perform FFT in aplurality of different sizes based on a detected FFT mode. In an aspect,a multi-mode transform module may include a plurality of FFT modules,each configured to use different FFT sizes, the output of each of whichmay be selected based on a detected FFT mode.

As discussed above with respect to FIGS. 2 and 3, the wireless device202 a can be configured to operate in various FFT modes. In variousembodiments, the wireless device 202 a can be configured to use a64-point FFT size in conjunction with a higher-bandwidth channel thanthe 32-point FFT channel. For example, the 64-point FFT channel can havetwice the bandwidth of the 32-point FFT channel. In an embodiment, thetransform module 304 can be configured to use a 64-point FFT size inconjunction with a 2 MHz channel, and the transform module 304 can beconfigured to use a 32-point FFT channel can be a 1 MHz channel. In anembodiment, the transform module 304 can be configured to selectivelyuse a plurality of different FFT sizes. In another embodiment, aplurality of different IFFTs can each be configured to use a differentFFT size, the output of which can be selectively routed to the DAC 306.

In some embodiments, the data unit 500 may include a Partial airidentifier (AID) or PAID field. The PAID field includes a partialidentifier for one or more receivers or STAs 106. The PAID field may beused by each STA 106 as an early indicator of whether the STA 106 shouldreceive and decode the remainder of the data unit 500. For example, ifthe PAID field indicates that the data unit 500 is not intended for aparticular STA 106, that STA 106 may discontinue processing the dataunit 500 in order to save power.

In some embodiments, the PAID field includes a unique identification ofthe STA 106, such as a full local identifier (e.g., an AID) of the STA106. In some embodiments, the PAID field includes a partial localidentifier of the STA 106, such as a portion of the AID, for example,some number of least significant bits (LSBs) of the AID. In someembodiments, the PAID field includes a partial local identifier of theSTA 106 and a partial local identifier of the associated BSS or the AP104.

In some embodiments, the PAID field is not explicitly transmitted, butis encoded in another field, such as a cyclic redundancy check (CRC)field. For example, a CRC may be calculated with the PAID field andother fields of the data unit 500 which are transmitted. The STA 106receives the transmitted fields and the CRC field. The STA 106 thencalculates a CRC based on the received fields and the PAID field whichindicates that the STA 106 should continue processing the data unit 500.If the CRC calculated by the STA 106 matches the CRC received, the STA106 continues processing the data unit 500.

In some embodiments, the data unit 500 includes multiple sets ofparameters. A first set of parameters may include parameters used todetermine how long the STA 106 is in a power down mode if the data unit500 is not intended for the STA 106. A second set of parameters mayinclude other parameters of the data unit 500, such as those discussedbelow. The PAID field may be included in the second set. In someembodiments, each of the sets of parameters is covered by an independentCRC specific to that set. Each STA 106 determines based on the PAIDfield whether the data unit 500 is to be decoded. If the data unit 500is not to be decoded, the STA 106 defers for a time based on theinformation in the first set of parameters. In some embodiments, theCRCs are in the SIG field. In some embodiments, the CRC of the secondset of parameters is in the service field after the preamble, forexample if the data unit 500 is for non-AMPDU.

In some embodiments, the PAID field is in the service field. In suchembodiments, the PAID field may be sent with the same MCS as the data inthe SIG field. In some embodiments, the PAID field may immediatelyprecede the MAC header.

In some embodiments, the data unit 500 includes a random seed for use bythe STA 106 to descramble the data. In some embodiments, at least aportion of the PAID field may also be the seed. In some embodiments, theSTA 106 may recognize multiple, for example, consecutive, PAID fields asnew seeds for retransmissions.

In some embodiments, the data unit 500 includes no service field. Insuch embodiments the bandwidth may be indicated, for example, in the SIGfield or in the MAC header. Similarly, a CRC may be included, forexample, in the SIG field or in the MAC header. Additionally, oralternatively, the random seed may be included, for example, in the SIGfield or in the MAC header. In some embodiments, the random seed mayalso be included in the PAID field.

In some embodiments, the PAID field is scrambled with the data in theSIG field and the scrambled sequence is covered by a CRC. Alternatively,the PAID field may be appended to the SIG field and the set is coveredby a CRC.

In some embodiments, the PAID field is not static over multipletransmissions to a STA 106. For example, the PAID field may change eachtransmission or may change after each number of transmissions. The PAIDfield may be changed according to an algorithm common to both thetransmitting device and the receiving STA 106. For example, the next ina series of numbers can be used. In some embodiments, the next PAIDfield value is equal to the previous PAID field value plus one. In someembodiments, the algorithm includes generating the PAID field based inpart on the timing synchronization function (TSF) or a hash of the TSFof the network. The calculations of the PAID field may occur, forexample, every second, every 2, 3, 4, 5, or other number of seconds,every minute, every 2, 3, 4, 5, or other number of minutes. Accordingly,errors due to TSF misalignment will be rare.

In some embodiments, the receiving STA 106 communicates to thetransmitting device the PAID field value or an indication of the PAIDfield value to use for a next transmission. For example, the next PAIDfield value or an indication of the next PAID field value may beincluded in an ACK sent in response to a received transmission from thetransmitting device.

For example, in a first data unit, the AP 104 uses a default PAID fieldvalue, to which the STA 106 responds by decoding the first data unit.The STA 106 sends an ACK to acknowledge receipt of the first data unit.In the ACK communication, the STA 106 indicates a next PAID field value.Subsequently, in a second data unit, the AP 104 uses the next PAID fieldvalue, to which the STA 106 responds by decoding the second data unit.

The default PAID field value may be, for example, a broadcast PAID fieldvalue or may be, for example, a PAID field value associated with theparticular STA 106 to which the first and second data units areintended. The next PAID field value may, for example, be a next in aseries of numbers or may, for example, be a hash of at least a portionof the first data unit, such as the data of the first data unit.

In some embodiments, if the AP 104 does not receive the ACK, the AP 104may transmit the second data unit using the default PAID field value orthe latest PAID field value for which an ACK was received. Accordingly,the STA 106 may be configured to decode data units which include any ofmultiple PAID field values. For example, the STA 106 may be configuredto decode data units which include any of the default PAID field value,the PAID field value for the latest received and decoded data unit, andthe PAID field value indicated in the latest ACK transmitted by the STA106. In such embodiments, the AP 104 may be configured to select one ofthe multiple PAID field values for the STA 106. Such selection, may, forexample, be random or pseudorandom.

In some embodiments, the PAID field is assigned by the AP 104 with, forexample, a management exchange. For example, the PAID field may bereassigned periodically. In some embodiments, the STA 106 may request orassign a new PAID field for a next transmission from the AP 104. Forexample, if a STA 106 decodes multiple data units which are not intendedfor that STA 106, the STA 106 may request or designate a new PAID fieldvalue.

In some systems, unicast packet filtering is possible through MACaddress. In such systems, the PAID field may be useful in enhancingpacket filtering based on packet content.

In some embodiments, the PAID field may identify a type of the dataunit. In some embodiments, the PAID field may additionally identify thecontent of the data unit. For example, if the data unit includes atraffic indication map (TIM) for a group of STAs, the PAID field mayidentify the group of STAs the data unit is intended for. In someembodiments, certain values of the PAID field may be used to indicatethat the data unit is a beacon and to identify the beacon changesequence number. If the STA is already up to date the STA can ignore theremainder of the data unit after processing the PAID field.

In an embodiment, for 64-point FFT signals, the data unit 500 caninclude a 240 μs preamble 510. The preamble 510 can include a single2-symbol STF 512, a single 2-symbol LTF 514, and a 2-symbol SIGNAL unit520. The SIGNAL unit 520 can include one or more of the fields shownbelow in Table 1. Although the fields are shown having a particularlength, and in a particular order, in various embodiments, one or morefields may be rearranged, added, omitted, or may have a differentlength. In some embodiments, the SIGNAL unit 520 has all of the fieldsshown in Table 1. In some embodiments, the SIGNAL unit 520 has only thefields shown in Table 1. In some embodiments, the SIGNAL unit 520 hasthe fields shown in Table 1 in the order shown in Table 1. In someembodiments, at least a portion of the information of multiple fieldsshown in Table 1 is included in a single field. For example, the firstand second fields of Table 1 may be collapsed into a single fieldincluding the information of both the first and second fields.

TABLE 1 Field of SIG-A (64-Point FFT) Bits MCS 4 Num SS 2 SGI 1 Length12 Aggregation 1 BW 2 Coding 1 AID 12 STBC 1 Smoothing 1 Reserved 1 CRC4 Tail 6 Total 48

In the aspect shown in Table 1, the SIGNAL unit 520 can include an “MCS”field indicating the modulation coding scheme (MCS) used. The “MCS”field can be O-bits long. In an embodiment, the “MCS” field may indicatethat, for example, quadrature phase-shift keying (QPSK) is used. TheSIGNAL unit 520 can further include a “Num SS” field indicating thenumber of spatial streams used. The “Num SS” field can be 2-bits long.The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 12-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 4095 bytes. The SIGNAL unit 520 can further include an“aggregation” field indicating whether A-MPDU is being used. The“aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “BW” field indicating thebandwidth (BW) used. The “BW” field can be 2-bits long. In variousembodiments, the 2-bit “BW” field can indicate whether the bandwidth is2 MHz, 4 MHz, 8 MHz, or 16 MHz. The SIGNAL unit 520 can further includea “coding” field indicating the type of encoding used. The “coding”field can be 1-bit long.

The SIGNAL unit 520 can further include an “AID” field indicating theair identification (AID) associated with the data unit 500. The “AID”field can be 12-bits long. The SIGNAL unit 520 can further include a“STBC” field indicating whether space-time block coding (STBC) is used.The “STBC” field can be 1-bit long. The SIGNAL unit 520 can furtherinclude a “smoothing” field indicating whether smoothing is recommendedon channel estimation. The “smoothing” field can be 1-bit long.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

The SIGNAL unit 520 can further include one or more reserved bits. Asshown in the implementation of Table 1, the SIGNAL unit 520 can include1 reserved bit. As discussed below, in various embodiments, the reservedbits can be used to carry additional information for different packettypes. For example, the reserved bits can include additional informationrelated to acknowledgement (ACK) packets. In some embodiments, one ormore of the reserved bits are used as one or more Doppler mitigationbits to signal to the receiver that there are sections in SIGNAL unit520 which can enable the receiver to mitigate the impact of ‘hightemporal channel variation’ during transmission of the SIGNAL unit 520.

In an embodiment, the SIGNAL unit 520 can include one or more of thefields shown below in Table 2. Although the fields are shown having aparticular length, and in a particular order, in various embodiments,one or more fields may be rearranged, added, omitted, or may have adifferent length. In some embodiments, the SIGNAL unit 520 has all ofthe fields shown in Table 2. In some embodiments, the SIGNAL unit 520has only the fields shown in Table 2. In some embodiments, the SIGNALunit 520 has the fields shown in Table 2 in the order shown in Table 2.In some embodiments, at least a portion of the information of multiplefields shown in Table 2 is included in a single field. For example, thefirst and second fields of Table 2 may be collapsed into a single fieldincluding the information of both the first and second fields.

TABLE 2 Field of SIG-A (64-Point FFT) Bits MCS 4 Num SS 2 SGI 1 Length12 Aggregation 1 BW 2 Coding 1 AID 13 STBC 1 Beamformed 1 Reserved 0 CRC8 Tail 6 Total 52

In the aspect shown in Table 2, the SIGNAL unit 520 can include an “MCS”field indicating the modulation coding scheme (MCS) used. The “MCS”field can be O-bits long. In an embodiment, the “MCS” field may indicatethat, for example, quadrature phase-shift keying (QPSK) is used. TheSIGNAL unit 520 can further include a “Num SS” field indicating thenumber of spatial streams used. The “Num SS” field can be 2-bits long.The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 12-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 4095 bytes. The SIGNAL unit 520 can further include an“aggregation” field indicating whether A-MPDU is being used. The“aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “BW” field indicating thebandwidth (BW) used. The “BW” field can be 2-bits long. In variousembodiments, the 2-bit “BW” field can indicate whether the bandwidth is2 MHz, 4 MHz, 8 MHz, or 16 MHz. The SIGNAL unit 520 can further includea “coding” field indicating the type of encoding used. The “coding”field can be 1-bit long.

The SIGNAL unit 520 can further include an “AID” field indicating theair identification (AID) associated with the data unit 500. The “AID”field can be 13-bits long. In some embodiments, the “AID” field carriesthe AID for SU, whereas for MU, the first bit is reserved, the next 6bits carry group identifier (GID), and the last 6 bits carry a number ofspace time streams (N_(sts)) for 2^(nd), 3^(rd) and 4^(th) users. Insome embodiments, certain exceptional values of the “AID” field may beused to identify the specific content of the packet, for example,whether the packet is for multicast or broadcast. The SIGNAL unit 520can further include a “STBC” field indicating whether space-time blockcoding (STBC) is used. The “STBC” field can be 1-bit long. The SIGNALunit 520 can further include a “beamformed” field indicating whether abeamforming steering matrix is applied to the waveform in an SUtransmission. The “beamformed” field can be 1-bit long.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 8-bits or 4-bits long. Inan embodiment, another error-detection code can be used instead of, orin addition to, the CRC. The SIGNAL unit 520 can further include a“tail” field used to reset the state of a convolution encoder and/ordecoder. The “tail” field can be 6-bits long.

The SIGNAL unit 520 can further include one or more reserved bits. TheSIGNAL unit 520 can include, for example, 0 or 4 reserved bits. Asdiscussed below, in various embodiments, the reserved bits can be usedto carry additional information for different packet types. For example,the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, one or more of thereserved bits are used as one or more Doppler mitigation bits to signalto the receiver that there are sections in SIGNAL unit 520 which canenable the receiver to mitigate the impact of ‘high temporal channelvariation’ during transmission of the SIGNAL unit 520.

In an embodiment, for 32-point FFT signals, the data unit 500 caninclude a 360 μs preamble. The preamble can include a single 4-symbolSTF 512, a single 2-symbol LTF 514, and a 3-symbol SIGNAL unit 520. TheSIGNAL unit 520 can include one or more of the fields shown below inTable 3. Although the fields are shown having a particular length, andin a particular order, in various embodiments, one or more fields may berearranged, added, omitted, or may have a different length. In someembodiments, the SIGNAL unit 520 has all of the fields shown in Table 3.In some embodiments, the SIGNAL unit 520 has only the fields shown inTable 3. In some embodiments, the SIGNAL unit 520 has the fields shownin Table 3 in the order shown in Table 3. In some embodiments, at leasta portion of the information of multiple fields shown in Table 3 isincluded in a single field. For example, the first and second fields ofTable 3 may be collapsed into a single field including the informationof both the first and second fields.

TABLE 3 Field of SIG-A (32-Point FFT) Bits MCS 4 Num SS 2 SGI 1 Length11 Aggregation 1 Coding 1 STBC 1 Reserved 5 CRC 4 Tail 6 Total 36

In the aspect shown in Table 3, the SIGNAL unit 520 can include an “MCS”field indicating the modulation coding scheme (MCS) used. The “MCS”field can be 4-bits long. In an embodiment, the “MCS” field may indicatethat, for example, quadrature phase-shift keying (QPSK) is used. TheSIGNAL unit 520 can further include a “Num SS” field indicating thenumber of spatial streams used. The “Num SS” field can be 2-bits long.The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 11-bit long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 4095 bytes. The SIGNAL unit 520 can further include an“aggregation” field indicating whether A-MPDU is being used. The“aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 1-bit long. The SIGNALunit 520 can further include a “STBC” field indicating whetherspace-time block coding (STBC) is used. The “STBC” field can be 1-bitlong.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

The SIGNAL unit 520 can further include one or more reserved bits. Asshown in the implementation of Table 3, the SIGNAL unit 520 can include5 reserved bits. As discussed below, in various embodiments, thereserved bits can be used to carry additional information for differentpacket types. For example, the reserved bits can include additionalinformation related to acknowledgement (ACK) packets. In someembodiments, one or more of the reserved bits are used as one or moreDoppler mitigation bits to signal to the receiver that there aresections in SIGNAL unit 520 which can enable the receiver to mitigatethe impact of ‘high temporal channel variation’ during transmission ofthe SIGNAL unit 520.

In the implementation shown in Table 3, the SIGNAL unit 520 for a32-point FFT can omit one or more fields used in the SIGNAL unit 520 forthe 64-point FFT shown above in Table 1. For example, the “BW,” “AID,”and “smoothing” fields are omitted. In an embodiment, certain fields canbe omitted because the receiving device may implicitly know theparameters indicated in those fields.

In various embodiments, symbols, fields, and/or data units can berepeated in order to increase the effective signal-to-noise ratio (SNR)of a transmission. For example, 32-point FFT transmissions can berepeated two times, three times, four times, eight times, etc. In anembodiment, repetition can be accomplished in conjunction withdownclocking of the transmission.

In one embodiment, for 32-point FFT signals with a two-time repetitionmode, the data unit 500 can include a 440 μs preamble. The preamble caninclude a single 4-symbol STF 512, a single 3-symbol LTF 514, and a4-symbol SIGNAL unit 520. The SIGNAL unit 520 can include one or more ofthe fields shown below in Table 4. Although the fields are shown havinga particular length, and in a particular order, in various embodiments,one or more fields may be rearranged, added, omitted, or may have adifferent length. In some embodiments, the SIGNAL unit 520 has all ofthe fields shown in Table 4. In some embodiments, the SIGNAL unit 520has only the fields shown in Table 4. In some embodiments, the SIGNALunit 520 has the fields shown in Table 4 in the order shown in Table 4.In some embodiments, at least a portion of the information of multiplefields shown in Table 4 is included in a single field. For example, thefirst and second fields of Table 4 may be collapsed into a single fieldincluding the information of both the first and second fields.

TABLE 4 Field of SIG-A (32-Point FFT, 2x Repetition) Bits Length 9Reserved 8 Parity 1 Tail 6 Total 24

In the aspect shown in Table 4, the SIGNAL unit 520 can include a“length” field indicating length of the payload 530. The “length” fieldcan be 9-bits long. In an embodiment, the “length” field can indicatethe length of the payload 530 in units of symbols when A-MPDU is beingused. The “length” field can indicate the length of the payload 530 inunits of bytes when A-MPDU is not being used. In an embodiment, A-MPDUis used for packed sizes greater than 4095 bytes.

The SIGNAL unit 520 can further include a “parity” field indicating theresult of a parity calculated on one or more fields of the SIGNAL unit520. The “parity” field can be 1-bit long. In an embodiment, anothererror-detection code can be used instead of, or in addition to, theparity bit. The SIGNAL unit 520 can further include a “tail” field usedto reset the state of a convolution encoder and/or decoder. The “tail”field can be 6-bits long.

The SIGNAL unit 520 can further include one or more reserved bits. Asshown in the implementation of Table 4, the SIGNAL unit 520 can include8 reserved bits. As discussed below, in various embodiments, thereserved bits can be used to carry additional information for differentpacket types. For example, the reserved bits can include additionalinformation related to acknowledgement (ACK) packets. In someembodiments, one or more of the reserved bits are used as one or moreDoppler mitigation bits to signal to the receiver that there aresections in SIGNAL unit 520 which can enable the receiver to mitigatethe impact of ‘high temporal channel variation’ during transmission ofthe SIGNAL unit 520.

In the implementation shown in Table 4, the SIGNAL unit 520 for a32-point FFT can omit one or more fields used in the SIGNAL unit 520 forthe 64-point FFT shown above in Table 1. For example, the “MCS,” “NumSS,” “SGI,” “BW,” “AID,” “aggregation,” “coding,” and “STBC” fields areomitted. In an embodiment, certain fields can be omitted because thereceiving device may implicitly know the parameters indicated in thosefields.

In an embodiment, a single SIGNAL unit 520 format can be used for32-point FFT in both non-repetition and two-time repetition modes. Thesingle SIGNAL unit 520 can be included in a “combined” preamble. In anembodiment, the combined preamble can be 520 μs long. The preamble caninclude a single 4-symbol STF 512, a single 3-symbol LTF 514, and a6-symbol SIGNAL unit 520. The SIGNAL unit 520 can include one or more ofthe fields shown below in Table 5. Although the fields are shown havinga particular length, and in a particular order, in various embodiments,one or more fields may be rearranged, added, omitted, or may have adifferent length. In some embodiments, the SIGNAL unit 520 has all ofthe fields shown in Table 5. In some embodiments, the SIGNAL unit 520has only the fields shown in Table 5. In some embodiments, the SIGNALunit 520 has the fields shown in Table 5 in the order shown in Table 5.In some embodiments, at least a portion of the information of multiplefields shown in Table 5 is included in a single field. For example, thefirst and second fields of Table 5 may be collapsed into a single fieldincluding the information of both the first and second fields.

TABLE 5 Field of SIG-A (32-Point FFT Combined) Bits MCS 4 Num SS 2 SGI 1Length 11 Aggregation 1 Coding 1 STBC 1 Smoothing 1 Reserved 4 CRC 4Tail 6 Total 36

In the aspect shown in Table 5, the SIGNAL unit 520 can include an “MCS”field indicating the modulation coding scheme (MCS) used. The “MCS”field can be 4-bits long. In an embodiment, the “MCS” field may indicatethat, for example, quadrature phase-shift keying (QPSK) is used. TheSIGNAL unit 520 can further include a “Num SS” field indicating thenumber of spatial streams used. The “Num SS” field can be 2-bits long.The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 11-bit long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 4095 bytes. The SIGNAL unit 520 can further include an“aggregation” field indicating whether A-MPDU is being used. The“aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 1-bit long. The SIGNALunit 520 can further include a “STBC” field indicating whetherspace-time block coding (STBC) is used. The “STBC” field can be 1-bitlong. The SIGNAL unit 520 can further include a “smoothing” fieldindicating whether smoothing is recommended on channel estimation. The“smoothing” field can be 1-bit long.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

The SIGNAL unit 520 can further include one or more reserved bits. Asshown in the implementation of Table 5, the SIGNAL unit 520 can include4 reserved bits. As discussed below, in various embodiments, thereserved bits can be used to carry additional information for differentpacket types. For example, the reserved bits can include additionalinformation related to acknowledgement (ACK) packets. In someembodiments, one or more of the reserved bits are used as one or moreDoppler mitigation bits to signal to the receiver that there aresections in SIGNAL unit 520 which can enable the receiver to mitigatethe impact of ‘high temporal channel variation’ during transmission ofthe SIGNAL unit 520.

In the implementation shown in Table 5, the SIGNAL unit 520 for a32-point FFT can omit one or more fields used in the SIGNAL unit 520 forthe 64-point FFT shown above in Table 1. For example, the “BW” and the“AID” fields are omitted. In an embodiment, certain fields can beomitted because the receiving device may implicitly know the parametersindicated in those fields.

In an embodiment, a single SIGNAL unit 520 format can be used for32-point FFT in normal and 2x rep modes. The SIGNAL unit 520 can includeone or more of the fields shown below in Table 6. Although the fieldsare shown having a particular length, and in a particular order, invarious embodiments, one or more fields may be rearranged, added,omitted, or may have a different length. In some embodiments, the SIGNALunit 520 has all of the fields shown in Table 6. In some embodiments,the SIGNAL unit 520 has only the fields shown in Table 6. In someembodiments, the SIGNAL unit 520 has the fields shown in Table 6 in theorder shown in Table 6. In some embodiments, at least a portion of theinformation of multiple fields shown in Table 6 is included in a singlefield. For example, the first and second fields of Table 6 may becollapsed into a single field including the information of both thefirst and second fields.

TABLE 6 Field of SIG-A (32-Point FFT normal and 2x repetition modes)Bits MCS 4 Num SS 2 SGI 1 Length 11 Aggregation 1 Coding 1 STBC 1Beamformed 1 Reserved 0 CRC 8 Tail 6 Total 36

In the aspect shown in Table 6, the SIGNAL unit 520 can include an “MCS”field indicating the modulation coding scheme (MCS) used. The “MCS”field can be O-bits long. In an embodiment, the “MCS” field may indicatethat, for example, quadrature phase-shift keying (QPSK) is used. TheSIGNAL unit 520 can further include a “Num SS” field indicating thenumber of spatial streams used. The “Num SS” field can be 2-bits long.The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 11-bit long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 2047 bytes. The SIGNAL unit 520 can further include an“aggregation” field indicating whether A-MPDU is being used. The“aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 1-bit long. The SIGNALunit 520 can further include a “STBC” field indicating whetherspace-time block coding (STBC) is used. The “STBC” field can be 1-bitlong. The SIGNAL unit 520 can further include a “beamformed” fieldindicating whether a beamforming steering matrix is applied to thewaveform in an SU transmission. The “beamformed” field can be 1-bitlong.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits or 8-bits long. Inan embodiment, another error-detection code can be used instead of, orin addition to, the CRC. The SIGNAL unit 520 can further include a“tail” field used to reset the state of a convolution encoder and/ordecoder. The “tail” field can be 6-bits long.

The SIGNAL unit 520 can further include one or more reserved bits. TheSIGNAL unit 520 can include, for example, 0 or 4 reserved bits. Asdiscussed below, in various embodiments, the reserved bits can be usedto carry additional information for different packet types. For example,the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, one or more of thereserved bits are used as one or more Doppler mitigation bits to signalto the receiver that there are sections in SIGNAL unit 520 which canenable the receiver to mitigate the impact of ‘high temporal channelvariation’ during transmission of the SIGNAL unit 520.

In the implementation shown in Table 6, the SIGNAL unit 520 for a32-point FFT can omit one or more fields used in the SIGNAL unit 520 forthe 64-point FFT shown above in Table 1. For example, the “BW” and the“AID” fields are omitted. In an embodiment, certain fields can beomitted because the receiving device may implicitly know the parametersindicated in those fields.

In an embodiment, a single SIGNAL unit 520 format can be used for a64-point FFT SIG-B MU mode. The SIGNAL unit 520 can be sent for eachuser with precoding applied. The SIGNAL unit 520 can include one or moreof the fields shown below in Table 7. Although the fields are shownhaving a particular length, and in a particular order, in variousembodiments, one or more fields may be rearranged, added, omitted, ormay have a different length. In some embodiments, the SIGNAL unit 520has all of the fields shown in Table 7. In some embodiments, the SIGNALunit 520 has only the fields shown in Table 7. In some embodiments, theSIGNAL unit 520 has the fields shown in Table 7 in the order shown inTable 7. In some embodiments, at least a portion of the information ofmultiple fields shown in Table 7 is included in a single field. Forexample, the first and second fields of Table 7 may be collapsed into asingle field including the information of both the first and secondfields.

TABLE 7 Field of SIG-B (64-Point FFT MU mode) Bits MCS 4 Coding 1Reserved 11 CRC 4 Tail 6 Total 26

In the aspect shown in Table 7, the SIGNAL unit 520 can include an “MCS”field indicating the modulation coding scheme (MCS) used. The “MCS”field can be O-bits long. In an embodiment, the “MCS” field may indicatethat, for example, quadrature phase-shift keying (QPSK) is used. TheSIGNAL unit 520 can further include a “coding” field indicating the typeof encoding used. The “coding” field can be 1-bit long.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

The SIGNAL unit 520 can further include one or more reserved bits. TheSIGNAL unit 520 can include, for example, 11 reserved bits. As discussedbelow, in various embodiments, the reserved bits can be used to carryadditional information for different packet types. For example, thereserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, one or more of thereserved bits are used as one or more Doppler mitigation bits to signalto the receiver that there are sections in SIGNAL unit 520 which canenable the receiver to mitigate the impact of ‘high temporal channelvariation’ during transmission of the SIGNAL unit 520.

In the implementation shown in Table 7, the SIGNAL unit 520 for a32-point FFT can omit one or more fields used in the SIGNAL unit 520 forthe 64-point FFT shown above in Table 1. For example, the “BW” and the“AID” fields are omitted. In an embodiment, certain fields can beomitted because the receiving device may implicitly know the parametersindicated in those fields.

In an embodiment, for 2 MHz, 64-point FFT signals, the data unit 500 cansupport multiple users. The preamble can include a 2-symbol SIGNAL unit520. The SIGNAL unit 520 can include one or more of the fields shownbelow in Table 8. Although the fields are shown having a particularlength, and in a particular order, in various embodiments, one or morefields may be rearranged, added, omitted, or may have a differentlength. In some embodiments, the SIGNAL unit 520 has all of the fieldsshown in Table 8. In some embodiments, the SIGNAL unit 520 has only thefields shown in Table 8. In some embodiments, the SIGNAL unit 520 hasthe fields shown in Table 8 in the order shown in Table 8. In someembodiments, at least a portion of the information of multiple fieldsshown in Table 8 is included in a single field. For example, the firstand second fields of Table 8 may be collapsed into a single fieldincluding the information of both the first and second fields.

TABLE 8 Field of SIG-A (64-Point FFT) Bits BW 2 1^(st) Reserved 1 STBC 1Num SS 2 AID/GID + Nsts 12 2^(nd) Reserved 1 SGI 1 Coding 1 MCS 4Beamformed 1 Aggregation 1 Length 12 3^(rd) Reserved 3 CRC 4 Tail 6Total 52

In some embodiments, a first symbol of the SIGNAL unit 520 includes the“BW,” “1^(st) Reserved,” “STBC,” “Num SS,” “AID/GID+Nsts,” “2^(nd)Reserved,” “SGI,” “Coding,” “MCS,” and “Beamformed,” fields, and asecond symbol of the SIGNAL unit 520 includes the “Aggregation,”“Length,” “3^(rd) Reserved,” “CRC,” and “Tail” fields.

In the aspect shown in Table 8, the SIGNAL unit 520 can include a “BW”field indicating the bandwidth (BW) used. The “BW” field can be 2-bitslong. In various embodiments, the 2-bit “BW” field can indicate whetherthe bandwidth is 2 MHz, 4 MHz, 8 MHz, or 16 MHz. The SIGNAL unit 520 canfurther include a “1^(st) Reserved” bit. The SIGNAL unit 520 can furtherinclude a “STBC” field indicating whether space-time block coding (STBC)is used. The “STBC” field can be 1-bit long.

The SIGNAL unit 520 can further include a “Num SS” field indicating thenumber of spatial streams used. The “Num SS” field can be 2-bits long.The SIGNAL unit 520 can further include an “AID/GID+Nsts” fieldindicating the air identification (AID) associated with the data unit500. The “AID/GID+Nsts” field can be 12-bits long. In some embodiments,the “AID/GID+Nsts” field carries the AID for SU, whereas for MU, thefirst 6 bits carry GID, and the last 6 bits carry N_(sts) for 2^(nd),3^(rd) and 4^(th) users. In some embodiments, certain exceptional valuesof the “AID/GID+Nsts” field may be used to identify the specific contentof the packet, for example, whether the packet is for multicast orbroadcast. During SU mode, the “AID” bits of the “AID/GID+Nsts” fieldcan be used for embodiments which use cellular offload, so that otherdevices can save power during the transmissions. The SIGNAL unit 520 canfurther include a “2^(nd) Reserved” bit.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 1-bit long. The SIGNALunit 520 can further include an “MCS” field indicating the modulationcoding scheme (MCS) used. The “MCS” field can be 4-bits long. In anembodiment, the “MCS” field may indicate that, for example, quadraturephase-shift keying (QPSK) is used. The SIGNAL unit 520 can furtherinclude a “beamformed” field indicating whether a beamforming steeringmatrix is applied to the waveform in an SU transmission. The“beamformed” field can be 1-bit long.

The SIGNAL unit 520 can further include an “aggregation” fieldindicating whether A-MPDU is being used. The “aggregation” field can be1-bit long. The SIGNAL unit 520 can further include a “length” fieldindicating length of the payload 530. The “length” field can be 12-bitslong. In an embodiment, the “length” field can indicate the length ofthe payload 530 in units of symbols when A-MPDU is being used.

The “length” field can indicate the length of the payload 530 in unitsof bytes when A-MPDU is not being used. In an embodiment, A-MPDU is usedfor packed sizes greater than 4095 bytes. The SIGNAL unit 520 canfurther include 3 “3^(rd) Reserved” bits. In alternative embodiments,the “length” field is 9-bits long and the SIGNAL unit 520 includes 6“3^(rd) Reserved” bits.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

As discussed below, in various embodiments, the reserved bits can beused to carry additional information for different packet types. Forexample, the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, the reserved bitscan be used to extend the preceding field. For example, in the exampleshown in Table 8, the “1^(st) Reserved” bit may be used as a 3^(rd) bitfor the “BW” field, the “2^(nd) Reserved bit may be used as a 13^(th)bit for the “AID/GID+Nsts” field, and/or one or more of the “3^(rd)Reserved” bits may be used as additional bits for the “Length” field. Insome embodiments, one or more of the reserved bits are used as one ormore Doppler mitigation bits to signal to the receiver that there aresections in SIGNAL unit 520 which can enable the receiver to mitigatethe impact of ‘high temporal channel variation’ during transmission ofthe SIGNAL unit 520.

In an embodiment, a single SIGNAL unit 520 format can be used for a64-point FFT SIG-B MU mode. The SIGNAL unit 520 can include one or moreof the fields shown below in Table 9. Although the fields are shownhaving a particular length, and in a particular order, in variousembodiments, one or more fields may be rearranged, added, omitted, ormay have a different length. In some embodiments, the SIGNAL unit 520has all of the fields shown in Table 9. In some embodiments, the SIGNALunit 520 has only the fields shown in Table 9. In some embodiments, theSIGNAL unit 520 has the fields shown in Table 9 in the order shown inTable 9. In some embodiments, at least a portion of the information ofmultiple fields shown in Table 9 is included in a single field. Forexample, the first and second fields of Table 9 may be collapsed into asingle field including the information of both the first and secondfields.

TABLE 9 Field of SIG-B (64-Point FFT MU mode) Bits MCS 4 Coding 1Reserved 7 CRC 8 Tail 6 Total 26

In the aspect shown in Table 9, the SIGNAL unit 520 can include an “MCS”field indicating the modulation coding scheme (MCS) used. The “MCS”field can be O-bits long. In an embodiment, the “MCS” field may indicatethat, for example, quadrature phase-shift keying (QPSK) is used. TheSIGNAL unit 520 can further include a “coding” field indicating the typeof encoding used. The “coding” field can be 1-bit long.

The SIGNAL unit 520 can further include 7 reserved bits. The SIGNAL unit520 can further include a “CRC” field indicating the result of a cyclicredundancy check (CRC) computed on one or more fields of the SIGNAL unit520. The “CRC” field can be 8-bits long. In an embodiment, anothererror-detection code can be used instead of, or in addition to, the CRC.The SIGNAL unit 520 can further include a “tail” field used to reset thestate of a convolution encoder and/or decoder. The “tail” field can be6-bits long.

As discussed below, in various embodiments, the reserved bits can beused to carry additional information for different packet types. Forexample, the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, one or more of thereserved bits are used as one or more Doppler mitigation bits to signalto the receiver that there are sections in SIGNAL unit 520 which canenable the receiver to mitigate the impact of ‘high temporal channelvariation’ during transmission of the SIGNAL unit 520.

In an embodiment, for a 1 MHz SIG-A packet, the SIGNAL unit 520 caninclude one or more of the fields shown below in Table 10. Although thefields are shown having a particular length, and in a particular order,in various embodiments, one or more fields may be rearranged, added,omitted, or may have a different length. In some embodiments, the SIGNALunit 520 has all of the fields shown in Table 10. In some embodiments,the SIGNAL unit 520 has only the fields shown in Table 10. In someembodiments, the SIGNAL unit 520 has the fields shown in Table 10 in theorder shown in Table 10. In some embodiments, at least a portion of theinformation of multiple fields shown in Table 10 is included in a singlefield. For example, the first and second fields of Table 10 may becollapsed into a single field including the information of both thefirst and second fields.

TABLE 10 Field of SIG-A (1 MHz 6 symbols) Bits STBC 1 Num SS 2 SGI 1Coding 1 Beamformed 1 MCS 4 Aggregation 1 Length 11 Reserved 4 CRC 4Tail 6 Total 36

In the aspect shown in Table 10, the SIGNAL unit 520 can include a“STBC” field indicating whether space-time block coding (STBC) is used.The “STBC” field can be 1-bit long. The SIGNAL unit 520 can furtherinclude a “Num SS” field indicating the number of spatial streams used.The “Num SS” field can be 2-bits long.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 1-bit long. The SIGNALunit 520 can further include a “beamformed” field indicating whether abeamforming steering matrix is applied to the waveform in an SUtransmission. The “beamformed” field can be 1-bit long.

The SIGNAL unit 520 can further include an “MCS” field indicating themodulation coding scheme (MCS) used. The “MCS” field can be 4-bits long.In an embodiment, the “MCS” field may indicate that, for example,quadrature phase-shift keying (QPSK) is used. The SIGNAL unit 520 canfurther include an “aggregation” field indicating whether A-MPDU isbeing used. The “aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 11-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 2047 bytes.

The SIGNAL unit 520 can further include 4 reserved bits. The SIGNAL unit520 can further include a “CRC” field indicating the result of a cyclicredundancy check (CRC) computed on one or more fields of the SIGNAL unit520. The “CRC” field can be 4-bits long. In an embodiment, anothererror-detection code can be used instead of, or in addition to, the CRC.The SIGNAL unit 520 can further include a “tail” field used to reset thestate of a convolution encoder and/or decoder. The “tail” field can be6-bits long.

As discussed below, in various embodiments, the reserved bits can beused to carry additional information for different packet types. Forexample, the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, the reserved bitscan be used to extend the preceding field. For example, in the exampleshown in Table 10, the reserved bits may be used as additional bits forthe “Length” field. In some embodiments, one or more of the reservedbits are used as one or more Doppler mitigation bits to signal to thereceiver that there are sections in SIGNAL unit 520 which can enable thereceiver to mitigate the impact of ‘high temporal channel variation’during transmission of the SIGNAL unit 520.

In an embodiment, for a 1 MHz SIG-A packet, the SIGNAL unit 520 caninclude one or more of the fields shown below in Table 11. Although thefields are shown having a particular length, and in a particular order,in various embodiments, one or more fields may be rearranged, added,omitted, or may have a different length. In some embodiments, the SIGNALunit 520 has all of the fields shown in Table 11. In some embodiments,the SIGNAL unit 520 has only the fields shown in Table 11. In someembodiments, the SIGNAL unit 520 has the fields shown in Table 11 in theorder shown in Table 11. In some embodiments, at least a portion of theinformation of multiple fields shown in Table 11 is included in a singlefield. For example, the first and second fields of Table 11 may becollapsed into a single field including the information of both thefirst and second fields.

TABLE 11 Field of SIG-A (1 MHz 5 symbols) Bits STBC 1 Num SS 2 SGI 1Coding 1 Beamformed 1 MCS 4 Aggregation 1 Length 9 Reserved 0 CRC 4 Tail6 Total 30

In the aspect shown in Table 11, the SIGNAL unit 520 can include a“STBC” field indicating whether space-time block coding (STBC) is used.The “STBC” field can be 1-bit long. The SIGNAL unit 520 can furtherinclude a “Num SS” field indicating the number of spatial streams used.The “Num SS” field can be 2-bits long.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 1-bit long. The SIGNALunit 520 can further include a “beamformed” field indicating whether abeamforming steering matrix is applied to the waveform in an SUtransmission. The “beamformed” field can be 1-bit long.

The SIGNAL unit 520 can further include an “MCS” field indicating themodulation coding scheme (MCS) used. The “MCS” field can be 4-bits long.In an embodiment, the “MCS” field may indicate that, for example,quadrature phase-shift keying (QPSK) is used. The SIGNAL unit 520 canfurther include an “aggregation” field indicating whether A-MPDU isbeing used. The “aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes.

The SIGNAL unit 520 can further include 0 reserved bits. The SIGNAL unit520 can further include a “CRC” field indicating the result of a cyclicredundancy check (CRC) computed on one or more fields of the SIGNAL unit520. The “CRC” field can be 4-bits long. In an embodiment, anothererror-detection code can be used instead of, or in addition to, the CRC.The SIGNAL unit 520 can further include a “tail” field used to reset thestate of a convolution encoder and/or decoder. The “tail” field can be6-bits long.

In an embodiment, for a 1 MHz SIG-A packet, the SIGNAL unit 520 caninclude one or more of the fields shown below in Table 12. Although thefields are shown having a particular length, and in a particular order,in various embodiments, one or more fields may be rearranged, added,omitted, or may have a different length. In some embodiments, the SIGNALunit 520 has all of the fields shown in Table 12. In some embodiments,the SIGNAL unit 520 has only the fields shown in Table 12. In someembodiments, the SIGNAL unit 520 has the fields shown in Table 12 in theorder shown in Table 12. In some embodiments, at least a portion of theinformation of multiple fields shown in Table 12 is included in a singlefield. For example, the first and second fields of Table 12 may becollapsed into a single field including the information of both thefirst and second fields.

TABLE 12 Field of SIG-A (1 MHz 5 symbols) Bits STBC 1 SGI 1 MCS 4 Coding1 Aggregation 1 Length 9 Reserved 3 CRC 4 Tail 6 Total 30

In the aspect shown in Table 12, the SIGNAL unit 520 can include a“STBC” field indicating whether space-time block coding (STBC) is used.The “STBC” field can be 1-bit long. The SIGNAL unit 520 can furtherinclude an “SGI” field indicating the short guard interval (SGI) used.The “SGI” field can be 1-bit long. In some embodiments, a short guardinterval may be 2 μs and a normal guard interval may be 8 μs. In someembodiments, a short guard interval may be 2 μs and a normal guardinterval may be 4 μs.

The SIGNAL unit 520 can further include an “MCS” field indicating themodulation coding scheme (MCS) used. The “MCS” field can be 4-bits long.In an embodiment, the “MCS” field may indicate that, for example,quadrature phase-shift keying (QPSK) is used. The SIGNAL unit 520 canfurther include a “coding” field indicating the type of encoding used.The “coding” field can be 1-bit long.

The SIGNAL unit 520 can further include an “aggregation” fieldindicating whether A-MPDU is being used. The “aggregation” field can be1-bit long. The SIGNAL unit 520 can further include a “length” fieldindicating length of the payload 530. The “length” field can be 9-bitslong. In an embodiment, the “length” field can indicate the length ofthe payload 530 in units of symbols when A-MPDU is being used. The“length” field can indicate the length of the payload 530 in units ofbytes when A-MPDU is not being used. In an embodiment, A-MPDU is usedfor packed sizes greater than 511 bytes.

The SIGNAL unit 520 can further include 3 reserved bits. The SIGNAL unit520 can further include a “CRC” field indicating the result of a cyclicredundancy check (CRC) computed on one or more fields of the SIGNAL unit520. The “CRC” field can be 4-bits long. In an embodiment, anothererror-detection code can be used instead of, or in addition to, the CRC.The SIGNAL unit 520 can further include a “tail” field used to reset thestate of a convolution encoder and/or decoder. The “tail” field can be6-bits long.

As discussed below, in various embodiments, the reserved bits can beused to carry additional information for different packet types. Forexample, the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, the reserved bitscan be used to extend the preceding field. For example, in the exampleshown in Table 12, one or more of the reserved bits may be used asadditional bits for the “Length” field. In some embodiments, one or moreof the reserved bits are used as one or more Doppler mitigation bits tosignal to the receiver that there are sections in SIGNAL unit 520 whichcan enable the receiver to mitigate the impact of ‘high temporal channelvariation’ during transmission of the SIGNAL unit 520.

In an embodiment, for a 1 MHz SIG-A packet, the SIGNAL unit 520 caninclude one or more of the fields shown below in Table 13. Although thefields are shown having a particular length, and in a particular order,in various embodiments, one or more fields may be rearranged, added,omitted, or may have a different length. In some embodiments, the SIGNALunit 520 has all of the fields shown in Table 13. In some embodiments,the SIGNAL unit 520 has only the fields shown in Table 13. In someembodiments, the SIGNAL unit 520 has the fields shown in Table 13 in theorder shown in Table 13. In some embodiments, at least a portion of theinformation of multiple fields shown in Table 13 is included in a singlefield. For example, the first and second fields of Table 13 may becollapsed into a single field including the information of both thefirst and second fields.

TABLE 13 Field of SIG-A (1 MHz 6 symbols) Bits STBC 1 SGI 1 MCS 4Aggregation 1 Length 9 Reserved 1 Parity 1 Tail 6 Total 24

In the aspect shown in Table 13, the SIGNAL unit 520 can include a“STBC” field indicating whether space-time block coding (STBC) is used.The “STBC” field can be 1-bit long. The SIGNAL unit 520 can furtherinclude an “SGI” field indicating the short guard interval (SGI) used.The “SGI” field can be 1-bit long. In some embodiments, a short guardinterval may be 2 μs and a normal guard interval may be 8 μs. In someembodiments, a short guard interval may be 2 μs and a normal guardinterval may be 4 μs.

The SIGNAL unit 520 can further include an “MCS” field indicating themodulation coding scheme (MCS) used. The “MCS” field can be 4-bits long.In an embodiment, the “MCS” field may indicate that, for example,quadrature phase-shift keying (QPSK) is used. The SIGNAL unit 520 canfurther include an “aggregation” field indicating whether A-MPDU isbeing used. The “aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes.

The SIGNAL unit 520 can further include 1 reserved bit. The SIGNAL unit520 can further include a “parity” field indicating the result of aparity calculated on one or more fields of the SIGNAL unit 520. The“parity” field can be 1-bit long. In an embodiment, anothererror-detection code can be used instead of, or in addition to, theparity bit. The SIGNAL unit 520 can further include a “tail” field usedto reset the state of a convolution encoder and/or decoder. The “tail”field can be 6-bits long.

As discussed below, in various embodiments, the reserved bit can be usedto carry additional information for different packet types. For example,the reserved bit can include additional information related toacknowledgement (ACK) packets. In some embodiments, the reserved bit canbe used to extend the preceding field. For example, in the example shownin Table 13, the reserved bit may be used as an additional bit for the“Length” field. In some embodiments, one or more of the reserved bitsare used as one or more Doppler mitigation bits to signal to thereceiver that there are sections in SIGNAL unit 520 which can enable thereceiver to mitigate the impact of ‘high temporal channel variation’during transmission of the SIGNAL unit 520.

In an embodiment, a single SIGNAL unit 520 format can be used for a64-point FFT SIG-B MU mode. The SIGNAL unit 520 can include one or moreof the fields shown below in Table 14. Although the fields are shownhaving a particular length, and in a particular order, in variousembodiments, one or more fields may be rearranged, added, omitted, ormay have a different length. In some embodiments, the SIGNAL unit 520has all of the fields shown in Table 14. In some embodiments, the SIGNALunit 520 has only the fields shown in Table 14. In some embodiments, theSIGNAL unit 520 has the fields shown in Table 14 in the order shown inTable 14. In some embodiments, at least a portion of the information ofmultiple fields shown in Table 14 is included in a single field. Forexample, the first and second fields of Table 14 may be collapsed into asingle field including the information of both the first and secondfields.

TABLE 14 Field of SIG-B (64-Point FFT MU mode) Bits MCS 4 Coding 1Length 9-11 Reserved 0-2  CRC 4 Tail 6 Total 26

In the aspect shown in Table 14, the SIGNAL unit 520 can include an“MCS” field indicating the modulation coding scheme (MCS) used. The“MCS” field can be O-bits long. In an embodiment, the “MCS” field mayindicate that, for example, quadrature phase-shift keying (QPSK) isused. The SIGNAL unit 520 can further include a “coding” fieldindicating the type of encoding used. The “coding” field can be 1-bitlong.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-11 bits long. Inan embodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. The SIGNAL unit 520 can further include 0-2 reservedbits. In an embodiment the total of the bits used for the Length fieldand the reserved bits is 11. In such embodiments, the reserved bits canbe used to extend the preceding field. For example, in the example shownin Table 14, the reserved bits may be used as additional bits for the“Length” field.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

As discussed below, in various embodiments, the reserved bits can beused to carry additional information for different packet types. Forexample, the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, one or more of thereserved bits are used as one or more Doppler mitigation bits to signalto the receiver that there are sections in SIGNAL unit 520 which canenable the receiver to mitigate the impact of ‘high temporal channelvariation’ during transmission of the SIGNAL unit 520.

In an embodiment, for 2 MHz, 64-point FFT signals, the data unit 500 cansupport multiple users. The preamble can include a 2-symbol SIGNAL unit520. The SIGNAL unit 520 can include one or more of the fields shownbelow in Table 15. Although the fields are shown having a particularlength, and in a particular order, in various embodiments, one or morefields may be rearranged, added, omitted, or may have a differentlength. In some embodiments, the SIGNAL unit 520 has all of the fieldsshown in Table 15. In some embodiments, the SIGNAL unit 520 has only thefields shown in Table 15. In some embodiments, the SIGNAL unit 520 hasthe fields shown in Table 15 in the order shown in Table 15. In someembodiments, at least a portion of the information of multiple fieldsshown in Table 15 is included in a single field. For example, the firstand second fields of Table 15 may be collapsed into a single fieldincluding the information of both the first and second fields.

TABLE 15 Field of SIG-A (64-Point FFT) Bits BW 2 1^(st) Reserved 1 STBC1 Num SS 2 AID/GID + Nsts 12 2^(nd) Reserved 1 SGI 1 Coding 2 MCS 4Beamformed 1 Aggregation 1 Length 9 3^(rd) Reserved 5 CRC 4 Tail 6 Total52

In some embodiments, a first symbol of the SIGNAL unit 520 includes the“BW,” “1^(st) Reserved,” “STBC,” “Num SS,” “AID/GID+Nsts,” “2^(nd)Reserved,” “SGI,” “Coding,” and “MCS,” fields, and a second symbol ofthe SIGNAL unit 520 includes the “Beamformed,” “Aggregation,” “Length,”“3^(rd) Reserved,” “CRC,” and “Tail” fields.

In the aspect shown in Table 15, the SIGNAL unit 520 can include a “BW”field indicating the bandwidth (BW) used. The “BW” field can be 2-bitslong. In various embodiments, the 2-bit “BW” field can indicate whetherthe bandwidth is 2 MHz, 4 MHz, 8 MHz, or 16 MHz. The SIGNAL unit 520 canfurther include a “1^(st) Reserved” bit. The SIGNAL unit 520 can furtherinclude a “STBC” field indicating whether space-time block coding (STBC)is used. The “STBC” field can be 1-bit long.

The SIGNAL unit 520 can further include a “Num SS” field indicating thenumber of spatial streams used. The “Num SS” field can be 2-bits long.The SIGNAL unit 520 can further include an “AID/GID+Nsts” fieldindicating the air identification (AID) associated with the data unit500. The “AID/GID+Nsts” field can be 12-bits long and may include a PAIDfield as discussed above. In some embodiments, the “AID/GID+Nsts” fieldcarries the AID for SU, whereas for MU, the first 6 bits carry GID, andthe last 6 bits carry N_(sts) for 2^(nd), 3^(rd) and 4^(th) users. Insome embodiments, certain exceptional values of the “AID/GID+Nsts” fieldmay be used to identify the specific content of the packet, for example,whether the packet is for multicast or broadcast. During SU mode, the“AID” bits of the “AID/GID+Nsts” field can be used for embodiments whichuse cellular offload, so that other devices can save power during thetransmissions. The SIGNAL unit 520 can further include a “2^(nd)Reserved” bit.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 2-bit long. The firstbit of the “coding” field can indicate coding type for a single user, orfor user 0 if multi-user. The second bit of the “coding” field can beused to indicate whether LDPC encoding resulted in an extra symbol. Ifmulti-user, the second bit of the “coding” field can be used to indicatewhether low-density parity-check (LDPC) encoding resulted in an extrasymbol for any of the users. The SIGNAL unit 520 can further include an“MCS” field indicating the modulation coding scheme (MCS) used. The“MCS” field can be 4-bits long. If multi-user, some bits of the “MCS”field may be used to indicate coding for users 1-3. For example, thefirst, second, and third bits of the “MCS” field may be used to indicatecoding for users 1, 2, and 3, respectively. In an embodiment, the “MCS”field may indicate that, for example, quadrature phase-shift keying(QPSK) is used.

The SIGNAL unit 520 can further include a “beamformed” field indicatingwhether a beamforming steering matrix is applied to the waveform in anSU transmission. The “beamformed” field can be 1-bit long. The SIGNALunit 520 can further include an “aggregation” field indicating whetherA-MPDU is being used. The “aggregation” field can be 1-bit long. TheSIGNAL unit 520 can further include a “length” field indicating lengthof the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes. The SIGNAL unit 520 can further include 5“3^(rd) Reserved” bits.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

As discussed below, in various embodiments, the reserved bits can beused to carry additional information for different packet types. Forexample, the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, the reserved bitscan be used to extend the preceding field. For example, in the exampleshown in Table 14, the “1^(st) Reserved” bit may be used as a 3^(rd) bitfor the “BW” field, the “2^(nd) Reserved bit may be used as a 13^(th)bit for the “AID/GID+Nsts” field, and/or one or more of the “3^(rd)Reserved” bits may be used as additional bits for the “Length” field. Insome embodiments, one or more of the reserved bits are used as one ormore Doppler mitigation bits to signal to the receiver that there aresections in SIGNAL unit 520 which can enable the receiver to mitigatethe impact of ‘high temporal channel variation’ during transmission ofthe SIGNAL unit 520.

In an embodiment, a single SIGNAL unit 520 format can be used for a64-point FFT SIG-B MU mode. The SIGNAL unit 520 can be sent for eachuser with precoding applied. The SIGNAL unit 520 can include one or moreof the fields shown below in Table 16. Although the fields are shownhaving a particular length, and in a particular order, in variousembodiments, one or more fields may be rearranged, added, omitted, ormay have a different length. In some embodiments, the SIGNAL unit 520has all of the fields shown in Table 16. In some embodiments, the SIGNALunit 520 has only the fields shown in Table 16. In some embodiments, theSIGNAL unit 520 has the fields shown in Table 16 in the order shown inTable 16. In some embodiments, at least a portion of the information ofmultiple fields shown in Table 16 is included in a single field. Forexample, the first and second fields of Table 16 may be collapsed into asingle field including the information of both the first and secondfields.

TABLE 16 Field of SIG-B (64-Point FFT MU mode) Bits MCS 4 Reserved 8 CRC8 Tail 6 Total 26

In the aspect shown in Table 16, the SIGNAL unit 520 can include an“MCS” field indicating the modulation coding scheme (MCS) used. The“MCS” field can be O-bits long. If multi-user, some bits of the “MCS”field may be used to indicate coding for users 1-3. For example, thefirst, second, and third bits of the “MCS” field may be used to indicatecoding for users 1, 2, and 3, respectively. In an embodiment, the “MCS”field may indicate that, for example, quadrature phase-shift keying(QPSK) is used.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 8-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

The SIGNAL unit 520 can further include one or more reserved bits. TheSIGNAL unit 520 can include, for example, 8 reserved bits. As discussedbelow, in various embodiments, the reserved bits can be used to carryadditional information for different packet types. For example, thereserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, one or more of thereserved bits are used as one or more Doppler mitigation bits to signalto the receiver that there are sections in SIGNAL unit 520 which canenable the receiver to mitigate the impact of ‘high temporal channelvariation’ during transmission of the SIGNAL unit 520.

In the implementation shown in Table 16, the SIGNAL unit 520 for a32-point FFT can omit one or more fields used in the SIGNAL unit 520 forthe 64-point FFT shown above in Table 1. For example, the “BW” and the“AID” fields are omitted. In an embodiment, certain fields can beomitted because the receiving device may implicitly know the parametersindicated in those fields.

In an embodiment, for a 1 MHz SIG-A packet, the SIGNAL unit 520 caninclude one or more of the fields shown below in Table 17. Although thefields are shown having a particular length, and in a particular order,in various embodiments, one or more fields may be rearranged, added,omitted, or may have a different length. In some embodiments, the SIGNALunit 520 has all of the fields shown in Table 17. In some embodiments,the SIGNAL unit 520 has only the fields shown in Table 17. In someembodiments, the SIGNAL unit 520 has the fields shown in Table 17 in theorder shown in Table 17. In some embodiments, at least a portion of theinformation of multiple fields shown in Table 17 is included in a singlefield. For example, the first and second fields of Table 17 may becollapsed into a single field including the information of both thefirst and second fields.

TABLE 17 Field of SIG-A (1 MHz 6 symbols) Bits STBC 1 Num SS 2 SGI 1Coding 2 Beamformed 1 MCS 4 Aggregation 1 Length 9 Reserved 5 CRC 4 Tail6 Total 36

In the aspect shown in Table 17, the SIGNAL unit 520 can include a“STBC” field indicating whether space-time block coding (STBC) is used.The “STBC” field can be 1-bit long. The SIGNAL unit 520 can furtherinclude a “Num SS” field indicating the number of spatial streams used.The “Num SS” field can be 2-bits long.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 2-bit long. The firstbit of the “coding” field can indicate coding type for a single user, orfor user 0 if multi-user. The second bit of the “coding” field can beused to indicate whether LDPC encoding resulted in an extra symbol. Ifmulti-user, the second bit of the “coding” field can be used to indicatewhether LDPC encoding resulted in an extra symbol for any of the users.The SIGNAL unit 520 can further include a “beamformed” field indicatingwhether a beamforming steering matrix is applied to the waveform in anSU transmission. The “beamformed” field can be 1-bit long.

The SIGNAL unit 520 can further include an “MCS” field indicating themodulation coding scheme (MCS) used. The “MCS” field can be 4-bits long.If multi-user, some bits of the “MCS” field may be used to indicatecoding for users 1-3. For example, the first, second, and third bits ofthe “MCS” field may be used to indicate coding for users 1, 2, and 3,respectively. In an embodiment, the “MCS” field may indicate that, forexample, quadrature phase-shift keying (QPSK) is used. The SIGNAL unit520 can further include an “aggregation” field indicating whether A-MPDUis being used. The “aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes.

The SIGNAL unit 520 can further include 5 reserved bits. The SIGNAL unit520 can further include a “CRC” field indicating the result of a cyclicredundancy check (CRC) computed on one or more fields of the SIGNAL unit520. The “CRC” field can be 4-bits long. In an embodiment, anothererror-detection code can be used instead of, or in addition to, the CRC.The SIGNAL unit 520 can further include a “tail” field used to reset thestate of a convolution encoder and/or decoder. The “tail” field can be6-bits long.

As discussed below, in various embodiments, the reserved bits can beused to carry additional information for different packet types. Forexample, the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, the reserved bitscan be used to extend the preceding field. For example, in the exampleshown in Table 17, one or more of the reserved bits may be used asadditional bits for the “Length” field. In some embodiments, one or moreof the reserved bits are used as one or more Doppler mitigation bits tosignal to the receiver that there are sections in SIGNAL unit 520 whichcan enable the receiver to mitigate the impact of ‘high temporal channelvariation’ during transmission of the SIGNAL unit 520.

In an embodiment, for a 1 MHz SIG-A packet, the SIGNAL unit 520 caninclude one or more of the fields shown below in Table 18. Although thefields are shown having a particular length, and in a particular order,in various embodiments, one or more fields may be rearranged, added,omitted, or may have a different length. In some embodiments, the SIGNALunit 520 has all of the fields shown in Table 18. In some embodiments,the SIGNAL unit 520 has only the fields shown in Table 18. In someembodiments, the SIGNAL unit 520 has the fields shown in Table 18 in theorder shown in Table 18. In some embodiments, at least a portion of theinformation of multiple fields shown in Table 18 is included in a singlefield. For example, the first and second fields of Table 18 may becollapsed into a single field including the information of both thefirst and second fields.

TABLE 18 Field of SIG-A (1 MHz 8 symbols) Bits STBC 1 Num SS 2 SGI 1Coding 2 Beamformed 1 MCS 4 Aggregation 1 AID 9-13 1^(st) Reserved 2-6 Length 9 2^(nd) Reserved 2 CRC 4 Tail 6 Total 48

In the aspect shown in Table 18, the SIGNAL unit 520 can include a“STBC” field indicating whether space-time block coding (STBC) is used.The “STBC” field can be 1-bit long. The SIGNAL unit 520 can furtherinclude a “Num SS” field indicating the number of spatial streams used.The “Num SS” field can be 2-bits long.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 2-bit long. The firstbit of the “coding” field can indicate coding type for a single user, orfor user 0 if multi-user. The second bit of the “coding” field can beused to indicate whether LDPC encoding resulted in an extra symbol. Ifmulti-user, the second bit of the “coding” field can be used to indicatewhether LDPC encoding resulted in an extra symbol for any of the users.The SIGNAL unit 520 can further include a “beamformed” field indicatingwhether a beamforming steering matrix is applied to the waveform in anSU transmission. The “beamformed” field can be 1-bit long.

The SIGNAL unit 520 can further include an “MCS” field indicating themodulation coding scheme (MCS) used. The “MCS” field can be 4-bits long.If multi-user, some bits of the “MCS” field may be used to indicatecoding for users 1-3. For example, the first, second, and third bits ofthe “MCS” field may be used to indicate coding for users 1, 2, and 3,respectively. In an embodiment, the “MCS” field may indicate that, forexample, quadrature phase-shift keying (QPSK) is used. The SIGNAL unit520 can further include an “aggregation” field indicating whether A-MPDUis being used. The “aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include an “AID” field indicating theair identification (AID) associated with the data unit 500. The “AID”field can be from 9 to 13-bits long and may include a PAID field asdiscussed above. The SIGNAL unit 520 can further include from 2 to 61^(st) reserved bits. The total of the bits for the “AID” field and the1^(st) reserved bits may be 15. The SIGNAL unit 520 can further includea “length” field indicating length of the payload 530. The “length”field can be 9-bits long. In an embodiment, the “length” field canindicate the length of the payload 530 in units of symbols when A-MPDUis being used. The “length” field can indicate the length of the payload530 in units of bytes when A-MPDU is not being used. In an embodiment,A-MPDU is used for packed sizes greater than 511 bytes.

The SIGNAL unit 520 can further include 2 2^(nd) reserved bits. TheSIGNAL unit 520 can further include a “CRC” field indicating the resultof a cyclic redundancy check (CRC) computed on one or more fields of theSIGNAL unit 520. The “CRC” field can be 4-bits long. In an embodiment,another error-detection code can be used instead of, or in addition to,the CRC. The SIGNAL unit 520 can further include a “tail” field used toreset the state of a convolution encoder and/or decoder. The “tail”field can be 6-bits long.

As discussed below, in various embodiments, the reserved bits can beused to carry additional information for different packet types. Forexample, the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, the reserved bitscan be used to extend the preceding field. For example, in the exampleshown in Table 18, one or more of the 1^(st) reserved bits may be usedas additional bits for the “AID” field, and one or more of the 2^(nd)reserved bits may be used as additional bits for the “Length” field. Insome embodiments, one or more of the reserved bits are used as one ormore Doppler mitigation bits to signal to the receiver that there aresections in SIGNAL unit 520 which can enable the receiver to mitigatethe impact of ‘high temporal channel variation’ during transmission ofthe SIGNAL unit 520.

In an embodiment, for a 1 MHz SIG-A packet, the SIGNAL unit 520 caninclude one or more of the fields shown below in Table 19. Although thefields are shown having a particular length, and in a particular order,in various embodiments, one or more fields may be rearranged, added,omitted, or may have a different length. In some embodiments, the SIGNALunit 520 has all of the fields shown in Table 19. In some embodiments,the SIGNAL unit 520 has only the fields shown in Table 19. In someembodiments, the SIGNAL unit 520 has the fields shown in Table 19 in theorder shown in Table 19. In some embodiments, at least a portion of theinformation of multiple fields shown in Table 19 is included in a singlefield. For example, the first and second fields of Table 19 may becollapsed into a single field including the information of both thefirst and second fields.

TABLE 19 Field of SIG-A (1 MHz 7 symbols) Bits STBC 1 Num SS 2 SGI 1Coding 2 Beamformed 1 MCS 4 Aggregation 1 AID 9 Reserved 2 Length 9 CRC4 Tail 6 Total 42

In the aspect shown in Table 19, the SIGNAL unit 520 can include a“STBC” field indicating whether space-time block coding (STBC) is used.The “STBC” field can be 1-bit long. The SIGNAL unit 520 can furtherinclude a “Num SS” field indicating the number of spatial streams used.The “Num SS” field can be 2-bits long.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 2-bit long. The firstbit of the “coding” field can indicate coding type for a single user, orfor user 0 if multi-user. The second bit of the “coding” field can beused to indicate whether LDPC encoding resulted in an extra symbol. Ifmulti-user, the second bit of the “coding” field can be used to indicatewhether LDPC encoding resulted in an extra symbol for any of the users.The SIGNAL unit 520 can further include a “beamformed” field indicatingwhether a beamforming steering matrix is applied to the waveform in anSU transmission. The “beamformed” field can be 1-bit long.

The SIGNAL unit 520 can further include an “MCS” field indicating themodulation coding scheme (MCS) used. The “MCS” field can be 4-bits long.If multi-user, some bits of the “MCS” field may be used to indicatecoding for users 1-3. For example, the first, second, and third bits ofthe “MCS” field may be used to indicate coding for users 1, 2, and 3,respectively. In an embodiment, the “MCS” field may indicate that, forexample, quadrature phase-shift keying (QPSK) is used. The SIGNAL unit520 can further include an “aggregation” field indicating whether A-MPDUis being used. The “aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include an “AID” field indicating theair identification (AID) associated with the data unit 500. The “AID”field can be 9-bits long and may include a PAID field as discussedabove. The SIGNAL unit 520 can further include 2 reserved bits. TheSIGNAL unit 520 can further include a “length” field indicating lengthof the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

As discussed below, in various embodiments, the reserved bits can beused to carry additional information for different packet types. Forexample, the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, the reserved bitscan be used to extend the preceding field. For example, in the exampleshown in Table 19, one or more of the reserved bits may be used asadditional bits for the “AID” field. In some embodiments, one or more ofthe reserved bits are used as one or more Doppler mitigation bits tosignal to the receiver that there are sections in SIGNAL unit 520 whichcan enable the receiver to mitigate the impact of ‘high temporal channelvariation’ during transmission of the SIGNAL unit 520.

In an embodiment, for a 1 MHz SIG-A packet, the SIGNAL unit 520 caninclude one or more of the fields shown below in Table 20. Although thefields are shown having a particular length, and in a particular order,in various embodiments, one or more fields may be rearranged, added,omitted, or may have a different length. In some embodiments, the SIGNALunit 520 has all of the fields shown in Table 20. In some embodiments,the SIGNAL unit 520 has only the fields shown in Table 20. In someembodiments, the SIGNAL unit 520 has the fields shown in Table 20 in theorder shown in Table 20. In some embodiments, at least a portion of theinformation of multiple fields shown in Table 20 is included in a singlefield. For example, the first and second fields of Table 20 may becollapsed into a single field including the information of both thefirst and second fields.

TABLE 20 Field of SIG-A (1 MHz 7 symbols) Bits STBC 1 Num SS 2 SGI 1Coding 2 Beamformed 1 MCS 4 Aggregation 1 AID 12 1^(st) Reserved 0-6Length 9 2^(nd) Reserved 0-6 CRC 4 Tail 6 Total 43-49

In the aspect shown in Table 20, the SIGNAL unit 520 can include a“STBC” field indicating whether space-time block coding (STBC) is used.The “STBC” field can be 1-bit long. The SIGNAL unit 520 can furtherinclude a “Num SS” field indicating the number of spatial streams used.The “Num SS” field can be 2-bits long.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 2-bit long. The firstbit of the “coding” field can indicate coding type for a single user, orfor user 0 if multi-user. The second bit of the “coding” field can beused to indicate whether LDPC encoding resulted in an extra symbol. Ifmulti-user, the second bit of the “coding” field can be used to indicatewhether LDPC encoding resulted in an extra symbol for any of the users.The SIGNAL unit 520 can further include a “beamformed” field indicatingwhether a beamforming steering matrix is applied to the waveform in anSU transmission. The “beamformed” field can be 1-bit long.

The SIGNAL unit 520 can further include an “MCS” field indicating themodulation coding scheme (MCS) used. The “MCS” field can be 4-bits long.If multi-user, some bits of the “MCS” field may be used to indicatecoding for users 1-3. For example, the first, second, and third bits ofthe “MCS” field may be used to indicate coding for users 1, 2, and 3,respectively. In an embodiment, the “MCS” field may indicate that, forexample, quadrature phase-shift keying (QPSK) is used. The SIGNAL unit520 can further include an “aggregation” field indicating whether A-MPDUis being used. The “aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include an “AID” field indicating theair identification (AID) associated with the data unit 500. The “AID”field can be 12-bits long and may include a PAID field as discussedabove. The SIGNAL unit 520 can further include 0-6 1^(St) reserved bits.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes. The SIGNAL unit 520 can further include 0-62^(nd) reserved bits.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

In an embodiment, for a 1 MHz SIG-A packet, the SIGNAL unit 520 caninclude one or more of the fields shown below in Table 21. Although thefields are shown having a particular length, and in a particular order,in various embodiments, one or more fields may be rearranged, added,omitted, or may have a different length. In some embodiments, the SIGNALunit 520 has all of the fields shown in Table 21. In some embodiments,the SIGNAL unit 520 has only the fields shown in Table 21. In someembodiments, the SIGNAL unit 520 has the fields shown in Table 21 in theorder shown in Table 21. In some embodiments, at least a portion of theinformation of multiple fields shown in Table 21 is included in a singlefield. For example, the first and second fields of Table 21 may becollapsed into a single field including the information of both thefirst and second fields.

TABLE 21 Field of SIG-A (1 MHz 7 symbols) Bits STBC 1 Num SS 2 SGI 1Coding 1 MCS 4 Aggregation 1 Length 9 Doppler/Reserved 1 CRC 4 Tail 0Total 24

In the aspect shown in Table 21, the SIGNAL unit 520 can include a“STBC” field indicating whether space-time block coding (STBC) is used.The “STBC” field can be 1-bit long. The SIGNAL unit 520 can furtherinclude a “Num SS” field indicating the number of spatial streams used.The “Num SS” field can be 2-bits long.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 1-bit long. The SIGNALunit 520 can further include an “MCS” field indicating the modulationcoding scheme (MCS) used. The “MCS” field can be 4-bits long. Ifmulti-user, some bits of the “MCS” field may be used to indicate codingfor users 1-3. For example, the first, second, and third bits of the“MCS” field may be used to indicate coding for users 1, 2, and 3,respectively. In an embodiment, the “MCS” field may indicate that, forexample, quadrature phase-shift keying (QPSK) is used. The SIGNAL unit520 can further include an “aggregation” field indicating whether A-MPDUis being used. The “aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes. The SIGNAL unit 520 can further include aDoppler/reserved bit, which may be used as a reserved bit or as aDoppler mitigation bit to signal to the receiver that there are sectionsin SIGNAL unit 520 which can enable the receiver to mitigate the impactof ‘high temporal channel variation’ during transmission of the SIGNALunit 520.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can omit a “tail” field usedto reset the state of a convolution encoder and/or decoder, and forexample, use tail biting, which is described more fully below.

In an embodiment, for a 2 MHz SIG packet with a short preamble, theSIGNAL unit 520 can include one or more of the fields shown below inTable 22. Although the fields are shown having a particular length, andin a particular order, in various embodiments, one or more fields may berearranged, added, omitted, or may have a different length. In someembodiments, the SIGNAL unit 520 has all of the fields shown in Table22. In some embodiments, the SIGNAL unit 520 has only the fields shownin Table 22. In some embodiments, the SIGNAL unit 520 has the fieldsshown in Table 22 in the order shown in Table 22. In some embodiments,at least a portion of the information of multiple fields shown in Table22 is included in a single field. For example, the first and secondfields of Table 22 may be collapsed into a single field including theinformation of both the first and second fields.

As discussed below, exceptional values in one or more of the fieldsshown in Table 22 may indicate that one or more fields of SIGNAL unit520 should be interpreted differently. For example, when one field inthe SIGNAL unit includes an exceptional state, one or more other fieldsof the SIGNAL unit 520 may include other information related toalternative frame type, such as an ACK frame, a beacon frame, a SYNCbeacon frame, a link adaptation frame, etc. Other information caninclude synchronization information, beacon information, link adaptationinformation, acknowledgment information, etc. In general, a zero-lengthpayload may be indicated by one or more fields in the SIGNAL unit 520having an exceptional state.

In one embodiment, a value of all-zeros in the “length” field of the 2MHz SIG packet may indicate that one or more of the reserved bits mayindicate an alternative frame type. In another embodiment, a value ofall-ones in the “MCS” field may indicate that the payload length iszero, and that one or more bits of the “length” field contains datarelated to an alternative frame type. In another embodiment, a non-zerovalue in one or more “reserved” bits may indicate that the payloadlength is zero, and that one or more bits of the “length” field containsdata related to an alternative frame type. In some embodiments,exceptional values in the “length” field can indicate how the SIG fieldshould be interpreted. In some embodiments, exceptional values in the“length” field can indicate the number of symbols of data following thePHY preamble, and optionally at what MCS the symbols are encoded.Exceptional values of the “length” field may include, for example, smalllengths, such as 0, 1, 2, 3, or values less than, for example, 5 or 10.

TABLE 22 Field of SIG (2 MHz 2 symbols) Bits Reserved 1 STBC 1 Reserved1 BW 2 Nsts 2 PAID 9 SGI 1 Coding 2 MCS 4 Smoothing 1 Aggregation 1Length 9 ACK Indication 2 Reserved 2 CRC 4 Tail 6 Total 48

In the aspect shown in Table 22, the SIGNAL unit 520 can include a first“Reserved” field that may be one bit long. The SIGNAL unit 520 canfurther include an “STBC” field indicating whether space-time blockcoding (STBC) is used. The “STBC” field can be 1-bit long. The SIGNALunit 520 can further include a second “Reserved” field that may be onebit in length.

The SIGNAL unit 520 can further include a “BW” field indicating thebandwidth (BW) used. The “BW” field can be 2-bits long. In variousembodiments, the 2-bit “BW” field can indicate whether the bandwidth is2 MHz, 4 MHz, 8 MHz, or 16 MHz. The SIGNAL unit 520 can further includean “Nsts” field. The “Nsts” field may provide the number of space timestreams (STS). The “Nsts” field may be two bits long.

The SIGNAL unit 520 can further include a “PAID” field indicating apartial association identifier associated with the data unit 500. The“PAID” field can be 9-bits long. The SIGNAL unit 520 can further includean “SGI” field indicating the short guard interval (SGI) used. The “SGI”field can be 1-bit long. In some embodiments, a short guard interval maybe 2 μs and a normal guard interval may be 8 μs. In some embodiments, ashort guard interval may be 2 μs and a normal guard interval may be 4μs.

The SIGNAL unit 520 can further include a “Coding” field indicating thetype of encoding used. The “Coding” field can be 2-bit long. The SIGNALunit 520 can further include an “MCS” field indicating the modulationcoding scheme (MCS) used. The “MCS” field can be 4-bits long. Ifmulti-user, some bits of the “MCS” field may be used to indicate codingfor users 1-3. For example, the first, second, and third bits of the“MCS” field may be used to indicate coding for users 1, 2, and 3,respectively. In an embodiment, the “MCS” field may indicate that, forexample, quadrature phase-shift keying (QPSK) is used. The SIGNAL unit520 can further include a “Smoothing” field indicating whether smoothingis recommended on channel estimation. The “Smoothing” field can be onebit long. The SIGNAL unit 520 can further include an “aggregation” fieldindicating whether A-MPDU is being used. The “aggregation” field can be1-bit long.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes. The SIGNAL unit 520 can further include an “ACKIndication” field indicating whether the SIGNAL unit is anacknowledgment. In an embodiment, the “ACK Indication” field mayindicate whether the SIGNAL unit 520 is an acknowledgement (0x00), ablock acknowledgement (0x01), or not an acknowledgement (0x10). Thevalue of (0x11) may be reserved. The “ACK Indication” field may be twobits in length. The SIGNAL unit may include a third “Reserved” field.The third “Reserved” field may be two bits in length.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

In an embodiment, the first “Reserved” field, “STBC” field, second“Reserved” field, “BW” field, “Nsts” field, “PAID” field, “SGI” field,“Coding” field, “MCS” field, and the “Smoothing” field may be encodedusing the first symbol of SIG-A. In an embodiment, the “Aggregation”field, “Length” field, “ACK Indication” field, third “Reserved” field,“CRC” field, and “Tail” field may be encoded using the second symbol ofSIG-A.

In an embodiment, for a 2 MHz SIG-A packet with a long preamble and usedfor a single user, the SIGNAL unit 520 can include one or more of thefields shown below in Table 23. Although the fields are shown having aparticular length, and in a particular order, in various embodiments,one or more fields may be rearranged, added, omitted, or may have adifferent length. In some embodiments, the SIGNAL unit 520 has all ofthe fields shown in Table 23. In some embodiments, the SIGNAL unit 520has only the fields shown in Table 23. In some embodiments, the SIGNALunit 520 has the fields shown in Table 23 in the order shown in Table23. In some embodiments, at least a portion of the information ofmultiple fields shown in Table 23 is included in a single field. Forexample, the first and second fields of Table 23 may be collapsed into asingle field including the information of both the first and secondfields.

As discussed below, exceptional values in one or more of the fieldsshown in Table 23 may indicate that one or more fields of SIGNAL unit520 should be interpreted differently. For example, when one field inthe SIGNAL unit 520 includes an exceptional state, one or more otherfields of the SIGNAL unit 520 may include other information related toalternative frame type, such as an ACK frame, a beacon frame, a SYNCbeacon frame, a link adaptation frame, etc. Other information caninclude synchronization information, beacon information, link adaptationinformation, acknowledgment information, etc. In general, a zero-lengthpayload may be indicated by one or more fields in the SIGNAL unit 520having an exceptional state.

In one embodiment, a value of all-zeros in the “length” field of the 2MHz SIG-A packet may indicate that one or more of the reserved bits mayindicate an alternative frame type. In another embodiment, a value ofall-ones in the “MCS” field may indicate that the payload length iszero, and that one or more bits of the “length” field contains datarelated to an alternative frame type. In another embodiment, a non-zerovalue in one or more “reserved” bits may indicate that the payloadlength is zero, and that one or more bits of the “length” field containsdata related to an alternative frame type. In some embodiments,exceptional values in the “length” field can indicate how the SIG fieldshould be interpreted. In some embodiments, exceptional values in the“length” field can indicate the number of symbols of data following thePHY preamble, and optionally at what MCS the symbols are encoded.Exceptional values of the “length” field may include, for example, smalllengths, such as 0, 1, 2, 3, or values less than, for example, 5 or 10.

TABLE 23 Field of SIG-A (2 MHz 2 symbols) Bits MU/SU 1 STBC 1 Reserved 1BW 2 Nsts 2 PAID 9 SGI 1 Coding 2 MCS 4 Beam-Change Indication 1Aggregation 1 Length 9 ACK Indication 2 Reserved 2 CRC 4 Tail 6 Total 48

In the aspect shown in Table 23, the SIGNAL unit 520 can include a“MU/SU” field, indicating whether the SIGNAL unit is for a single useror multiple users. The “MU/SU” field may be one bit long. The “MU/SU”field may be set to zero for single user. The SIGNAL unit 520 canfurther include an “STBC” field indicating whether space-time blockcoding (STBC) is used. The “STBC” field can be 1-bit long. The SIGNALunit 520 can further include a first “Reserved” field that may be onebit in length.

The SIGNAL unit 520 can further include a “BW” field indicating thebandwidth (BW) used. The “BW” field can be 2-bits long. In variousembodiments, the 2-bit “BW” field can indicate whether the bandwidth is2 MHz, 4 MHz, 8 MHz, or 16 MHz. The SIGNAL unit 520 can further includean “Nsts” field. The “Nsts” field may provide the number of space timestreams (STS). The “Nsts” field may be two bits long. The SIGNAL unit520 can further include a “PAID” field indicating a partial associationidentifier associated with the data unit 500. The “PAID” field can be9-bits long.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 2 bits long. In anembodiment, the first bit of the “Coding” field is the coding type forsingle user, while the second bit is the coding type for LDPC Nsymambiguity. The SIGNAL unit 520 can further include an “MCS” fieldindicating the modulation coding scheme (MCS) used. The “MCS” field canbe O-bits long. The “MCS” field may indicate coding for single-user. Ifmulti-user, some bits of the “MCS” field may be used to indicate codingfor users 1-3. For example, the first, second, and third bits of the“MCS” field may be used to indicate coding for users 1, 2, and 3,respectively. In an embodiment, the “MCS” field may indicate that, forexample, quadrature phase-shift keying (QPSK) is used. The SIGNAL unit520 can further include a “Beam-change indication” field indicating if aquadrature component matrix (Q matrix) changes starting data STF(D-STF). The “Beam-Change Indication” field can be one bit long. TheSIGNAL unit 520 can further include an “Aggregation” field indicatingwhether an A-MPDU is being used. The “Aggregation” field can be 1-bitlong.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes. The SIGNAL unit 520 can further include an “ACKIndication” field indicating whether the SIGNAL unit is anacknowledgment. In an embodiment, the “ACK Indication” field mayindicate whether the SIGNAL unit 520 is an acknowledgement (0x00), ablock acknowledgement (0x01), or not an acknowledgement (0x10). Thevalue of (0x11) may be reserved. The “ACK Indication” field may be twobits in length. The SIGNAL unit may include a second “Reserved” field.The “Reserved” field may be two bits in length.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

In an embodiment, the “MU/SU” field, “STBC” field, first “Reserved”field, “BW” field, “Nsts” field, “PAID” field, “SGI” field, “Coding”field, “MCS” field, and “Beam-Change Indication” field may be encodedusing the first symbol of SIG-A. In an embodiment, the “Aggregation”field, “Length” field, “ACK Indication” field, second “Reserved” field,“CRC” field, and “Tail” field may be encoded using the second symbol ofSIG-A.

In an embodiment, for a 2 MHz SIG-A packet with a long preamble and usedfor multi-user, the SIGNAL unit 520 can include one or more of thefields shown below in Table 24. Although the fields are shown having aparticular length, and in a particular order, in various embodiments,one or more fields may be rearranged, added, omitted, or may have adifferent length. In some embodiments, the SIGNAL unit 520 has all ofthe fields shown in Table 24. In some embodiments, the SIGNAL unit 520has only the fields shown in Table 24. In some embodiments, the SIGNALunit 520 has the fields shown in Table 24 in the order shown in Table24. In some embodiments, at least a portion of the information ofmultiple fields shown in Table 24 is included in a single field. Forexample, the first and second fields of Table 24 may be collapsed into asingle field including the information of both the first and secondfields.

As discussed below, exceptional values in one or more of the fieldsshown in Table 24 may indicate that one or more fields of SIGNAL unit520 should be interpreted differently. For example, when one field inthe SIGNAL unit includes an exceptional state, one or more other fieldsof the SIGNAL unit 520 may include other information related toalternative frame type, such as an ACK frame, a beacon frame, a SYNCbeacon frame, a link adaptation frame, etc. Other information caninclude synchronization information, beacon information, link adaptationinformation, acknowledgment information, etc. In general, a zero-lengthpayload may be indicated by one or more fields in the SIGNAL unit 520having an exceptional state.

In one embodiment, a value of all-zeros in the “length” field of the 2MHz SIG-A packet may indicate that one or more of the reserved bits mayindicate an alternative frame type. In another embodiment, a value ofall-ones in the “MCS” field may indicate that the payload length iszero, and that one or more bits of the “length” field contains datarelated to an alternative frame type. In another embodiment, a non-zerovalue in one or more “reserved” bits may indicate that the payloadlength is zero, and that one or more bits of the “length” field containsdata related to an alternative frame type. In some embodiments,exceptional values in the “length” field can indicate how the SIG fieldshould be interpreted. In some embodiments, exceptional values in the“length” field can indicate the number of symbols of data following thePHY preamble, and optionally at what MCS the symbols are encoded.Exceptional values of the “length” field may include, for example, smalllengths, such as 0, 1, 2, 3, or values less than, for example, 5 or 10.

TABLE 24 Field of SIG-A (2 MHz 2 symbols) Bits MU/SU 1 STBC 1 Reserved 1BW 2 Nsts 8 GID 6 SGI 1 Coding - I 4 Coding - II 1 Beam-ChangeIndication 1 Length 9 ACK Indication 2 Reserved 1 CRC 4 Tail 6 Total 48

In the aspect shown in Table 24, the SIGNAL unit 520 can include a“MU/SU” field, indicating whether the SIGNAL unit is for a single useror multiple users. The MU/SU″ field may be one bit long. The “MU/SU”field may be set to one for multi user. The SIGNAL unit 520 can furtherinclude an “STBC” field indicating whether space-time block coding(STBC) is used. The “STBC” field can be 1-bit long. The SIGNAL unit 520can further include a first “Reserved” field that may be one bit inlength.

The SIGNAL unit 520 can further include a “BW” field indicating thebandwidth (BW) used. The “BW” field can be 2-bits long. In variousembodiments, the 2-bit “BW” field can indicate whether the bandwidth is2 MHz, 4 MHz, 8 MHz, or 16 MHz. The SIGNAL unit 520 can further includean “Nsts” field. The “Nsts” field may provide the number of space timestreams (STS). The “Nsts” field may be eight bits long. Two bits of the“Nsts” field may be provided per user for up to four users. The SIGNALunit 520 can further include a “GID” field indicating a group identifierassociated with the data unit 500. The “GID” field can be 6-bits long.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “Coding-I” field indicatingthe type of encoding used. The “Coding-I” field can be 4 bits long. Eachbit may indicate a coding type for each of four users. The SIGNAL unit520 can further include a “Coding-II” field, indicating LDPC Nsymambiguity. The SIGNAL unit 520 can further include a “Beam-ChangeIndication” field indicating if a Q matrix changes starting D-STF. The“Beam-Change Indication” field can be one bit long.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes. The SIGNAL unit 520 can further include an “ACKIndication” field indicating whether the SIGNAL unit is anacknowledgment. In an embodiment, the “ACK Indication” field mayindicate whether the SIGNAL unit 520 is an acknowledgement (0x00), ablock acknowledgement (0x01), or not an acknowledgement (0x10). Thevalue of (0x11) may be reserved. The “ACK Indication” field may be twobits in length. The SIGNAL unit may include a second “Reserved” field.The “Reserved” field may be one bit in length.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

In an embodiment, the “MU/SU” field, “STBC” field, first “Reserved”field, “BW” field, “Nsts” field, “GID” field, “SGI” field, and the“Coding-I” field may be encoded using the first symbol of SIG-A. In anembodiment, the “Coding-II” field, “Beam-Change Indication” field,“Length” field, “ACK Indication” field, second “Reserved” field, “CRC”field, and “Tail” field may be encoded using the second symbol of SIG-A.

In an embodiment, for a 1 MHz SIG packet, the SIGNAL unit 520 caninclude one or more of the fields shown below in Table 25. Although thefields are shown having a particular length, and in a particular order,in various embodiments, one or more fields may be rearranged, added,omitted, or may have a different length. In some embodiments, the SIGNALunit 520 has all of the fields shown in Table 25. In some embodiments,the SIGNAL unit 520 has only the fields shown in Table 25. In someembodiments, the SIGNAL unit 520 has the fields shown in Table 25 in theorder shown in Table 25. In some embodiments, at least a portion of theinformation of multiple fields shown in Table 25 is included in a singlefield. For example, the first and second fields of Table 25 may becollapsed into a single field including the information of both thefirst and second fields.

As discussed below, exceptional values in one or more of the fieldsshown in Table 25 may indicate that one or more fields of SIGNAL unit520 should be interpreted differently. For example, when one field inthe SIGNAL unit includes an exceptional state, one or more other fieldsof the SIGNAL unit 520 may include other information related toalternative frame type, such as an ACK frame, a beacon frame, a SYNCbeacon frame, a link adaptation frame, etc. Other information caninclude synchronization information, beacon information, link adaptationinformation, acknowledgment information, etc. In general, a zero-lengthpayload may be indicated by one or more fields in the SIGNAL unit 520having an exceptional state.

In one embodiment, a value of all-zeros in the “length” field of the 1MHz SIG packet may indicate that one or more of the reserved bits mayindicate an alternative frame type. In another embodiment, a value ofall-ones in the “MCS” field may indicate that the payload length iszero, and that one or more bits of the “length” field contains datarelated to an alternative frame type. In another embodiment, a non-zerovalue in one or more “reserved” bits may indicate that the payloadlength is zero, and that one or more bits of the “length” field containsdata related to an alternative frame type. In some embodiments,exceptional values in the “length” field can indicate how the SIG fieldshould be interpreted. In some embodiments, exceptional values in the“length” field can indicate the number of symbols of data following thePHY preamble, and optionally at what MCS the symbols are encoded.Exceptional values of the “length” field may include, for example, smalllengths, such as 0, 1, 2, 3, or values less than, for example, 5 or 10.

TABLE 25 Field of SIG (1 MHz 5 or 6 symbols) Bits Nsts 2 SGI 1 Coding 2STBC 1 Reserved 1 MCS 4 Aggregation 1 Length 9 ACK Indication 2 Reserved3 CRC 4 Tail 6 Total 36

In the aspect shown in Table 25, the SIGNAL unit 520 can include an“Nsts” field. The “Nsts” field may provide the number of space timestreams (STS). The “Nsts” field may be two bits long. The SIGNAL unit520 can further include an “SGI” field indicating the short guardinterval (SGI) used. The “SGI” field can be 1-bit long. In someembodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “Coding” field indicating thetype of encoding used. The “Coding” field can be 2 bits long. One bitmay indicate a coding type (LDPC/BCC). The second bit may indicate LDPCN_(sym) ambiguity. The SIGNAL unit 520 can further include an “STBC”field indicating whether space-time block coding (STBC) is used. The“STBC” field can be 1-bit long. The SIGNAL unit 520 can further includea first “Reserved” field that may be one bit in length.

The SIGNAL unit 520 can further include an “MCS” field indicating themodulation coding scheme (MCS) used. The “MCS” field can be 4-bits long.In an embodiment, the “MCS” field may indicate that, for example,quadrature phase-shift keying (QPSK) is used. The SIGNAL unit 520 canfurther include an “Aggregation” field indicating whether an A-MPDU isbeing used. The “Aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes. The SIGNAL unit 520 can further include an “ACKIndication” field indicating whether the SIGNAL unit is anacknowledgment. In an embodiment, the “ACK Indication” field mayindicate whether the SIGNAL unit 520 is an acknowledgement (0x00), ablock acknowledgement (0x01), or not an acknowledgement (0x10). Thevalue of (0x11) may be reserved. The “ACK Indication” field may be twobits in length. The SIGNAL unit may include a second “Reserved” field.The “Reserved” field may be three bits in length.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

In an embodiment, one reserved bit is placed just after the firstsymbol. This may provision new PHY features. This provides a total offour (4) reserved bits.

In an embodiment, for a 2 MHz SIG packet with a short preamble, theSIGNAL unit 520 can include one or more of the fields shown below inTable 26. Although the fields are shown having a particular length, andin a particular order, in various embodiments, one or more fields may berearranged, added, omitted, or may have a different length.

The ordering of the fields may affect the peak to average power ratio ofreceiving or transmitting or generating the packet. Therefore, in someembodiments, the ordering of the fields may be changed to reduce thepeak to average power ratio experienced when receiving or transmittingor generating the packet. The peak to average power ratio for a packetwith the fields and field order shown in Table 26 has been measured. Themeasurements show a peak to average power ratio of 11.59 decibels forthe first symbol and 9.86 decibels for the second symbol when thereserved bits are set to one (1). When the reserved bits are set tozero, experimental results have shown a peak to average power ratio of13.4845 decibels for the first symbol and 10.4742 decibels for thesecond symbol when the reserved bits are set to zero (0).

In some embodiments, the SIGNAL unit 520 has all of the fields shown inTable 26. In some embodiments, the SIGNAL unit 520 has only the fieldsshown in Table 26. In some embodiments, the SIGNAL unit 520 has thefields shown in Table 26 in the order shown in Table 26. In someembodiments, at least a portion of the information of multiple fieldsshown in Table 26 is included in a single field. For example, the firstand second fields of Table 26 may be collapsed into a single fieldincluding the information of both the first and second fields.

As discussed below, exceptional values in one or more of the fieldsshown in Table 26 may indicate that one or more fields of SIGNAL unit520 should be interpreted differently. For example, when one field inthe SIGNAL unit includes an exceptional state, one or more other fieldsof the SIGNAL unit 520 may include other information related toalternative frame type, such as an ACK frame, a beacon frame, a SYNCbeacon frame, a link adaptation frame, etc. Other information caninclude synchronization information, beacon information, link adaptationinformation, acknowledgment information, etc. In general, a zero-lengthpayload may be indicated by one or more fields in the SIGNAL unit 520having an exceptional state.

In one embodiment, a value of all-zeros in the “length” field of the 2MHz SIG packet may indicate that one or more of the reserved bits mayindicate an alternative frame type. In another embodiment, a value ofall-ones in the “MCS” field may indicate that the payload length iszero, and that one or more bits of the “length” field contains datarelated to an alternative frame type. In another embodiment, a non-zerovalue in one or more “reserved” bits may indicate that the payloadlength is zero, and that one or more bits of the “length” field containsdata related to an alternative frame type. In some embodiments,exceptional values in the “length” field can indicate how the SIG fieldshould be interpreted. In some embodiments, exceptional values in the“length” field can indicate the number of symbols of data following thePHY preamble, and optionally at what MCS the symbols are encoded.Exceptional values of the “length” field may include, for example, smalllengths, such as 0, 1, 2, 3, or values less than, for example, 5 or 10.

TABLE 26 Field of SIG (2 MHz 2 symbols) Bits Reserved 1 STBC 1 Reserved1 BW 2 Nsts 2 Length 9 SGI 1 Coding 2 MCS 4 Smoothing 1 Aggregation 1PAID 9 ACK Indication 2 Reserved 2 CRC 4 Tail 6 Total 48

In the aspect shown in Table 26, the SIGNAL unit 520 can include a first“Reserved” field that may be one bit long. The SIGNAL unit 520 canfurther include an “STBC” field indicating whether space-time blockcoding (STBC) is used. The “STBC” field can be 1-bit long. The SIGNALunit 520 can further include a second “Reserved” field that may be onebit in length.

The SIGNAL unit 520 can further include a “BW” field indicating thebandwidth (BW) used. The “BW” field can be 2-bits long. In variousembodiments, the 2-bit “BW” field can indicate whether the bandwidth is2 MHz, 4 MHz, 8 MHz, or 16 MHz.

The SIGNAL unit 520 can further include an “Nsts” field. The “Nsts”field may provide the number of space time streams (STS). The “Nsts”field may be two bits long.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes. The SIGNAL unit 520 can further include an “SGI”field indicating the short guard interval (SGI) used. The “SGI” fieldcan be 1-bit long. In some embodiments, a short guard interval may be 2μs and a normal guard interval may be 8 μs. In some embodiments, a shortguard interval may be 2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “Coding” field indicating thetype of encoding used. The “Coding” field can be 2-bit long. The SIGNALunit 520 can further include an “MCS” field indicating the modulationcoding scheme (MCS) used. The “MCS” field can be 4-bits long. Ifmulti-user, some bits of the “MCS” field may be used to indicate codingfor users 1-3. For example, the first, second, and third bits of the“MCS” field may be used to indicate coding for users 1, 2, and 3,respectively. In an embodiment, the “MCS” field may indicate that, forexample, quadrature phase-shift keying (QPSK) is used. The SIGNAL unit520 can further include a “Smoothing” field indicating whether smoothingis recommended on channel estimation. The “Smoothing” field can be onebit long. The SIGNAL unit 520 can further include an “aggregation” fieldindicating whether A-MPDU is being used. The “aggregation” field can be1-bit long.

The SIGNAL unit 520 can further include a “PAID” field indicating apartial association identifier associated with the data unit 500. The“PAID” field can be 9-bits long. The SIGNAL unit 520 can further includean “ACK Indication” field indicating whether the SIGNAL unit is anacknowledgment. In an embodiment, the “ACK Indication” field mayindicate whether the SIGNAL unit 520 is an acknowledgement (0x00), ablock acknowledgement (0x01), or not an acknowledgement (0x10). Thevalue of (0x11) may be reserved. The “ACK Indication” field may be twobits in length. The SIGNAL unit may include a third “Reserved” field.The third “Reserved” field may be two bits in length.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

In an embodiment, the first “Reserved” field, “STBC” field, second“Reserved” field, “BW” field, “Nsts” field, “Length” field, “SGI” field,“Coding” field, “MCS” field, and the “Smoothing” field may be encodedusing the first symbol of SIG-A. In an embodiment, the “Aggregation”field, “PAID” field, “ACK Indication” field, third “Reserved” field,“CRC” field, and “Tail” field may be encoded using the second symbol ofSIG-A.

In an embodiment, one reserved bit is placed in the first symbol. Thismay provision new PHY features.

In an embodiment, generating or receiving a first symbol of a 2 MHz,short preamble SIG field with fields ordered as shown in Table 26 mayprovide a maximum peak to average power ratio (PAPR) of less than 7.1decibels. This PAPR may be measured using open loop transmission, a 256byte packet, aggregation off, the ACK Indication field set to ACK, onestream, MCS0 and MCS7. All combinations of the remaining unspecifiedfields may be considered when determining this PAPR. The CRC field usesthe four least significant bits (LSB) of the regular 8-bit CRC field in802.11n or 802.11ac. QBPSK modulation is used on both SIG symbols. 4xoversampled IFFT is also used. The stated maximum PAPR value above wasdetermined by measuring the PAPR over all combinations of theunspecified fields.

In an embodiment, for a 2 MHz SIG-A packet with a long preamble and usedfor a single user, the SIGNAL unit 520 can include one or more of thefields shown below in Table 27. Although the fields are shown having aparticular length, and in a particular order, in various embodiments,one or more fields may be rearranged, added, omitted, or may have adifferent length.

The ordering of the fields may affect the peak to average power ratio ofreceiving or transmitting or generating the packet. Therefore, in someembodiments, the ordering of the fields may be changed to reduce thepeak to average power ratio experienced when receiving or transmittingor generating the packet. The peak to average power ratio for a packetwith the fields and field order shown in Table 27 has been measured. Themeasurements show a peak to average power ratio of 11.1304 decibels forthe first symbol and 10.4442 decibels for the second symbol when thereserved bits are set to one (1). When the reserved bits are set tozero, experimental results have shown a peak to average power ratio of13.4845 decibels for the first symbol and 8.8606 decibels for the secondsymbol when the reserved bits are set to zero (0).

In some embodiments, the SIGNAL unit 520 has all of the fields shown inTable 27. In some embodiments, the SIGNAL unit 520 has only the fieldsshown in Table 27. In some embodiments, the SIGNAL unit 520 has thefields shown in Table 27 in the order shown in Table 27. In someembodiments, at least a portion of the information of multiple fieldsshown in Table 27 is included in a single field. For example, the firstand second fields of Table 27 may be collapsed into a single fieldincluding the information of both the first and second fields.

As discussed below, exceptional values in one or more of the fieldsshown in Table 27 may indicate that one or more fields of SIGNAL unit520 should be interpreted differently. For example, when one field inthe SIGNAL unit includes an exceptional state, one or more other fieldsof the SIGNAL unit 520 may include other information related toalternative frame type, such as an ACK frame, a beacon frame, a SYNCbeacon frame, a link adaptation frame, etc. Other information caninclude synchronization information, beacon information, link adaptationinformation, acknowledgment information, etc. In general, a zero-lengthpayload may be indicated by one or more fields in the SIGNAL unit 520having an exceptional state.

In one embodiment, a value of all-zeros in the “length” field of the 2MHz SIG-A packet may indicate that one or more of the reserved bits mayindicate an alternative frame type. In another embodiment, a value ofall-ones in the “MCS” field may indicate that the payload length iszero, and that one or more bits of the “length” field contains datarelated to an alternative frame type. In another embodiment, a non-zerovalue in one or more “reserved” bits may indicate that the payloadlength is zero, and that one or more bits of the “length” field containsdata related to an alternative frame type. In some embodiments,exceptional values in the “length” field can indicate how the SIG fieldshould be interpreted. In some embodiments, exceptional values in the“length” field can indicate the number of symbols of data following thePHY preamble, and optionally at what MCS the symbols are encoded.Exceptional values of the “length” field may include, for example, smalllengths, such as 0, 1, 2, 3, or values less than, for example, 5 or 10.

TABLE 27 Field of SIG-A (2 MHz 2 symbols) Bits MU/SU 1 STBC 1 Reserved 1BW 2 Nsts 2 Length 9 SGI 1 Coding 2 MCS 4 Beam-Change Indication 1Aggregation 1 PAID 9 ACK Indication 2 Reserved 2 CRC 4 Tail 6 Total 48

In the aspect shown in Table 27, the SIGNAL unit 520 can include a“MU/SU” field, indicating whether the SIGNAL unit is for a single useror multiple users. The “MU/SU” field may be one bit long. The “MU/SU”field may be set to zero for single user. The SIGNAL unit 520 canfurther include an “STBC” field indicating whether space-time blockcoding (STBC) is used. The “STBC” field can be 1-bit long. The SIGNALunit 520 can further include a first “Reserved” field that may be onebit in length.

The SIGNAL unit 520 can further include a “BW” field indicating thebandwidth (BW) used. The “BW” field can be 2-bits long. In variousembodiments, the 2-bit “BW” field can indicate whether the bandwidth is2 MHz, 4 MHz, 8 MHz, or 16 MHz. The SIGNAL unit 520 can further includean “Nsts” field. The “Nsts” field may provide the number of space timestreams (STS). The “Nsts” field may be two bits long.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “coding” field indicating thetype of encoding used. The “coding” field can be 2 bits long. In anembodiment, the first bit of the “Coding” field is the coding type forsingle user, while the second bit is the coding type for LDPC Nsymambiguity. The SIGNAL unit 520 can further include an “MCS” fieldindicating the modulation coding scheme (MCS) used. The “MCS” field canbe O-bits long. The “MCS” field may indicate coding for single-user. Ifmulti-user, some bits of the “MCS” field may be used to indicate codingfor users 1-3. For example, the first, second, and third bits of the“MCS” field may be used to indicate coding for users 1, 2, and 3,respectively. In an embodiment, the “MCS” field may indicate that, forexample, quadrature phase-shift keying (QPSK) is used. The SIGNAL unit520 can further include a “Beam-change indication” field indicating if aQ matrix changes starting D-STF. The “Beam-Change Indication” field canbe one bit long. The SIGNAL unit 520 can further include an“Aggregation” field indicating whether an A-MPDU is being used. The“Aggregation” field can be 1-bit long.

The SIGNAL unit 520 can further include a “PAID” field indicating apartial association identifier associated with the data unit 500. The“PAID” field can be 9-bits long.

The SIGNAL unit 520 can further include an “ACK Indication” fieldindicating whether the SIGNAL unit is an acknowledgment. In anembodiment, the “ACK Indication” field may indicate whether the SIGNALunit 520 is an acknowledgement (0x00), a block acknowledgement (0x01),or not an acknowledgement (0x10). The value of (0x11) may be reserved.The “ACK Indication” field may be two bits in length. The SIGNAL unitmay include a second “Reserved” field. The “Reserved” field may be twobits in length.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

In an embodiment, the “MU/SU” field, “STBC” field, first “Reserved”field, “BW” field, “Nsts” field, “Length” field, “SGI” field, “Coding”field, “MCS” field, and “Beam-Change Indication” field may be encodedusing the first symbol of SIG-A. In an embodiment, the “Aggregation”field, “PAID” field, “ACK Indication” field, second “Reserved” field,“CRC” field, and “Tail” field may be encoded using the second symbol ofSIG-A.

In an embodiment, generating or receiving a first symbol of a 2 MHz longpreamble single-user SIG-A field with fields ordered as described inTable 27 may result in a maximum peak to average power ratio that islower than 8.7 decibels. This PAPR may be measured using single user BFtransmission, a 256 byte packet, aggregation off, the ACK Indicationfield set to ACK, one stream, and MCS7. All combinations of theremaining unspecified fields may be considered when determining thisPAPR. The CRC field uses the four least significant bits (LSB) of theregular 8-bit CRC field in 802.11n or 802.11ac. QBPSK modulation is usedon both SIG symbols. 4x oversampled IFFT is also used. The maximum PAPRvalue above was determined by measuring the PAPR over all combinationsof the unspecified fields.

In an embodiment, for a 2 MHz SIG-A packet with a long preamble and usedfor multi-user, the SIGNAL unit 520 can include one or more of thefields shown below in Table 28. Although the fields are shown having aparticular length, and in a particular order, in various embodiments,one or more fields may be rearranged, added, omitted, or may have adifferent length. In some embodiments, the SIGNAL unit 520 has all ofthe fields shown in Table 28.

The ordering of the fields may affect the peak to average power ratio ofreceiving or transmitting or generating the packet. Therefore, in someembodiments, the ordering of the fields may be changed to reduce thepeak to average power ratio experienced when receiving or transmittingor generating the packet. The peak to average power ratio for a packetwith the fields and field order shown in Table 28 has been measured. Themeasurements show a peak to average power ratio of 11.8997 decibels forthe first symbol and 11.014 decibels for the second symbol when thereserved bits are set to one (1). When the reserved bits are set tozero, experimental results have shown a peak to average power ratio of10.6865 decibels for the first symbol and 11.8570 decibels for thesecond symbol when the reserved bits are set to zero (0).

In some embodiments, the SIGNAL unit 520 has only the fields shown inTable 28. In some embodiments, the SIGNAL unit 520 has the fields shownin Table 28 in the order shown in Table 28. In some embodiments, atleast a portion of the information of multiple fields shown in Table 28is included in a single field. For example, the first and second fieldsof Table 28 may be collapsed into a single field including theinformation of both the first and second fields.

As discussed below, exceptional values in one or more of the fieldsshown in Table 28 may indicate that one or more fields of SIGNAL unit520 should be interpreted differently. For example, when one field inthe SIGNAL unit includes an exceptional state, one or more other fieldsof the SIGNAL unit 520 may include other information related toalternative frame type, such as an ACK frame, a beacon frame, a SYNCbeacon frame, a link adaptation frame, etc. Other information caninclude synchronization information, beacon information, link adaptationinformation, acknowledgment information, etc. In general, a zero-lengthpayload may be indicated by one or more fields in the SIGNAL unit 520having an exceptional state.

In one embodiment, a value of all-zeros in the “length” field of the 2MHz SIG-A packet may indicate that one or more of the reserved bits mayindicate an alternative frame type. In another embodiment, a value ofall-ones in the “MCS” field may indicate that the payload length iszero, and that one or more bits of the “length” field contains datarelated to an alternative frame type. In another embodiment, a non-zerovalue in one or more “reserved” bits may indicate that the payloadlength is zero, and that one or more bits of the “length” field containsdata related to an alternative frame type. In some embodiments,exceptional values in the “length” field can indicate how the SIG fieldshould be interpreted. In some embodiments, exceptional values in the“length” field can indicate the number of symbols of data following thePHY preamble, and optionally at what MCS the symbols are encoded.Exceptional values of the “length” field may include, for example, smalllengths, such as 0, 1, 2, 3, or values less than, for example, 5 or 10.

TABLE 28 Field of SIG-A (2 MHz 2 symbols) Bits MU/SU 1 STBC 1 Reserved 1Nsts 8 BW 2 GID 6 SGI 1 Coding - I 4 Coding - II 1 Beam-ChangeIndication 1 Length 9 Ack Indication 2 Reserved 1 CRC 4 Tail 6 Total 48

In the aspect shown in Table 28, the SIGNAL unit 520 can include a“MU/SU” field, indicating whether the SIGNAL unit is for a single useror multiple users. The MU/SU” field may be one bit long. The “MU/SU”field may be set to one for multi user. The SIGNAL unit 520 can furtherinclude an “STBC” field indicating whether space-time block coding(STBC) is used. The “STBC” field can be 1-bit long. The SIGNAL unit 520can further include a first “Reserved” field that may be one bit inlength.

The SIGNAL unit 520 can further include an “Nsts” field. The “Nsts”field may provide the number of space time streams (STS). The “Nsts”field may be eight bits long. Two bits of the “Nsts” field may beprovided per user for up to four users. The SIGNAL unit 520 can furtherinclude a “BW” field indicating the bandwidth (BW) used. The “BW” fieldcan be 2-bits long. In various embodiments, the 2-bit “BW” field canindicate whether the bandwidth is 2 MHz, 4 MHz, 8 MHz, or 16 MHz. TheSIGNAL unit 520 can further include a “GID” field indicating a groupidentifier associated with the data unit 500. The “GID” field can be6-bits long.

The SIGNAL unit 520 can further include an “SGI” field indicating theshort guard interval (SGI) used. The “SGI” field can be 1-bit long. Insome embodiments, a short guard interval may be 2 μs and a normal guardinterval may be 8 μs. In some embodiments, a short guard interval may be2 μs and a normal guard interval may be 4 μs.

The SIGNAL unit 520 can further include a “Coding-I” field indicatingthe type of encoding used. The “Coding-I” field can be 4 bits long. Eachbit may indicate a coding type for each of four users. The SIGNAL unit520 can further include a “Coding-II” field, indicating LDPC Nsymambiguity. The SIGNAL unit 520 can further include a “Beam-ChangeIndication” field indicating if a Q matrix changes starting D-STF. The“Beam-Change Indication” field can be one bit long.

The SIGNAL unit 520 can further include a “length” field indicatinglength of the payload 530. The “length” field can be 9-bits long. In anembodiment, the “length” field can indicate the length of the payload530 in units of symbols when A-MPDU is being used. The “length” fieldcan indicate the length of the payload 530 in units of bytes when A-MPDUis not being used. In an embodiment, A-MPDU is used for packed sizesgreater than 511 bytes. The SIGNAL unit 520 can further include an “ACKIndication” field indicating whether the SIGNAL unit is anacknowledgment. In an embodiment, the “ACK Indication” field mayindicate whether the SIGNAL unit 520 is an acknowledgement (0x00), ablock acknowledgement (0x01), or not an acknowledgement (0x10). Thevalue of (0x11) may be reserved. The “ACK Indication” field may be twobits in length. The SIGNAL unit may include a second “Reserved” field.The “Reserved” field may be one bit in length.

The SIGNAL unit 520 can further include a “CRC” field indicating theresult of a cyclic redundancy check (CRC) computed on one or more fieldsof the SIGNAL unit 520. The “CRC” field can be 4-bits long. In anembodiment, another error-detection code can be used instead of, or inaddition to, the CRC. The SIGNAL unit 520 can further include a “tail”field used to reset the state of a convolution encoder and/or decoder.The “tail” field can be 6-bits long.

In an embodiment, the “MU/SU” field, “STBC” field, first “Reserved”field, “BW” field, “Nsts” field, “GID” field, “SGI” field, and the“Coding-I” field may be encoded using the first symbol of SIG-A. In anembodiment, the “Coding-II” field, “Beam-Change Indication” field,“Length” field, “ACK Indication” field, second “Reserved” field, “CRC”field, and “Tail” field may be encoded using the second symbol of SIG-A.

In an embodiment, generating or receiving a second symbol of an 8 MHzlong preamble multi-user SIG field with fields ordered as described inTable 28 may result in a maximum peak to average power ratio (PAPR) thatis lower than 11.1 decibels. This PAPR may be measured using multi-usertransmission with three users. The group ID is set to three (3). A 1500byte packet is used, with the ACK Indication field is set to block ACK(BA), one stream per user, and MCS7. All combinations of the remainingunspecified fields may be considered when determining this maximum PAPR.The CRC field uses the four least significant bits (LSB) of the regular8-bit CRC field in 802.11n or 802.11ac. QBPSK modulation is used on bothSIG symbols. 4x oversampled IFFT is also used. The stated maximum PAPRvalue is determined by measuring the PAPR over all combinations of theunspecified fields.

Because each of the seven symbols of the SIGNAL unit 520 is representedby a BPSK constellation having a rotation state which is either on thereal or on the imaginary axis, the rotation state of each of the symbolscan communicate an additional bit of information. For example, if thefirst symbol is on the real axis, this may communicate that STBC is on.Any of the bits of the SIGNAL unit 520 may be communicated throughsymbol rotation state. In the example shown in Table 28, at least onebit is communicated through rotation state of one of the symbols. Insome embodiments, up to six reserved bits may be communicated throughsymbol rotation state. The reserved bits communicated through symbolrotation state may be 1^(st) reserved bits, 2^(nd) reserved bits, or acombination of 1^(st) and 2^(nd) reserved bits. In some embodiments, forrobustness a single bit may be communicated by the rotation state ofmultiple symbols.

As discussed below, in various embodiments, the reserved bits can beused to carry additional information for different packet types. Forexample, the reserved bits can include additional information related toacknowledgement (ACK) packets. In some embodiments, the reserved bitscan be used to extend the preceding field. For example, in the exampleshown in Table 19, one or more of the reserved bits may be used asadditional bits for the “AID” field. In some embodiments, one or more ofthe reserved bits are used as one or more Doppler mitigation bits tosignal to the receiver that there are sections in SIGNAL unit 520 whichcan enable the receiver to mitigate the impact of ‘high temporal channelvariation’ during transmission of the SIGNAL unit 520.

In various embodiments, one or more fields in the SIGNAL unit 520 caninclude one or more “exceptional” states or values. An exceptional statecan include, for example, a field value that would not normally occur.For example, if the value of the “MCS” field can normally be either“00,” “01,” or “10,” then the value of all-ones (e.g., “11”) may beconsidered an exceptional state. As another example, a value ofall-zeros in the “length” field may be an exceptional state. As anotherexample, a non-zero value in any of the “reserved” bits may be anexceptional state.

Exceptional field states may indicate that one or more fields of theSIGNAL unit 520 should be interpreted differently. For example, when onefield in the SIGNAL unit includes an exceptional state, one or moreother fields of the SIGNAL unit 520 may include other informationrelated to alternative frame type, such as an ACK frame, a beacon frame,a SYNC beacon frame, a link adaptation frame, etc. Other information caninclude synchronization information, beacon information, link adaptationinformation, acknowledgment information, etc. In general, a zero-lengthpayload may be indicated by one or more fields in the SIGNAL unit 520having an exceptional state.

In one embodiment, a value of all-zeros in the “length” field mayindicate that one or more of the reserved bits may indicate analternative frame type. In another embodiment, a value of all-ones inthe “MCS” field may indicate that the payload length is zero, and thatone or more bits of the “length” field contains data related to analternative frame type. In another embodiment, a non-zero value in oneor more “reserved” bits may indicate that the payload length is zero,and that one or more bits of the “length” field contains data related toan alternative frame type. In some embodiments, exceptional values inthe “length” field can indicate how the SIG field should be interpreted.In some embodiments, exceptional values in the “length” field canindicate the number of symbols of data following the PHY preamble, andoptionally at what MCS the symbols are encoded. Exceptional values ofthe “length” field may include, for example, small lengths, such as 0,1, 2, 3, or values less than, for example, 5 or 10.

In some embodiments, an exceptional value in the “reserved” bitsindicates whether an ACK packet follows the current frame. In someimplementations, the “reserved” bits can indicate that the current frameis a control frame, and that the remaining bits are reserved for MACindications, including length.

TABLE 29 SIG field for short format preamble, 2 MHz and higher Field ofSIG (short format, 2 MHz+) Bits Description Reserved 1 STBC 1 Alamoutilike STBC on all or no streams Reserved 1 BW 2 Indicating BW mode (2, 4,8, or 16) Nsts 2 Length 9 Dual Interpretation based on Agg. bit SGI 1Short Guard Interval Coding 2 1^(st) bit for coding type, 2^(nd) bit forLDPC Nsym ambiguity MCS 4 Smoothing 1 Indicates Whether beamformingsteering matrix applied to waveform Aggregation bit 1 PAID 9 ACKIndication 2 00 = Ack; 01 = BA; 10 = No Ack; 11 = reserved Reserved 2CRC 4 Tail 6 Total 48

Table 29 illustrates an example of a SIG field that may be used in ashort format preamble in bandwidth modes of 2 MHz or higher. The firstten fields of the SIG field (i.e., Reserved, STBC, Reserved, BW, Nsts,Length, SGI, Coding, MCS, and Smoothing) may be in a first symbol of theSIG field and the last six fields of the SIG field (i.e., Aggregationbit, PAID, ACK Indication, Reserved, CRC, and Tail) may be in a secondsymbol of the SIG field. In a particular embodiment, at least onereserved bit may be included in the first symbol of the SIG field toprovision for a subsequently developed PHY feature.

TABLE 30 SIG-A field for long format preamble, 2 MHz and higher, SUField of SIG-A (long format, 2 MHz+, SU) Bits Description MU/SU bit 1Set to 0 for SU STBC 1 Alamouti like STBC on all or no streams Reserved1 BW 2 Indicating BW mode (2, 4, 8, or 16) Nsts 2 Length 9 DualInterpretation based on Agg. bit SGI 1 Short Guard Interval Coding 21^(st) bit for coding type, 2^(nd) bit for LDPC Nsym ambiguity MCS 4Beam-change 1 Whether Q matrix changes starting D-STF indication bitAggregation bit 1 PAID 9 ACK Indication 2 00 = Ack; 01 = BA; 10 = NoAck; 11 = reserved Reserved 2 CRC 4 Tail 6 Total 48

Table 30 illustrates an example of a SIG-A field that may be used in along format preamble in bandwidth modes of 2 MHz or higher for singleuser (SU) transmissions. The first ten fields of the SIG-A field (i.e.,MU/SU bit, STBC, Reserved, BW, Nsts, Length, SGI, Coding, MCS, andBeam-change indication bit) may be in a first symbol of the SIG-A fieldand the last six fields of the SIG-A field (i.e., Aggregation bit, PAID,ACK Indication, Reserved, CRC, and Tail) may be in a second symbol ofthe SIG-A field.

TABLE 31 SIG-A field for long format preamble, 2 MHz and higher, MUField of SIG-A (long format, 2 MHz+, MU) Bits Description MU/SU bit 1Set to 1 for MU STBC 1 Alamouti like STBC on all or no streams Reserved1 Nsts 8 2 bits per use for each of 4 users BW 2 Indicating BW mode (2,4, 8, or 16) GID 6 SGI 1 Short Guard Interval Coding-I 4 Coding type foreach of 4 users Coding-II 1 For LDPC Nsym ambiguity Reserved 1 Length 9Interpreted as number of symbols in MU case ACK Indication 2 00 = Ack;01 = BA; 10 = No Ack; 11 = reserved Reserved 1 CRC 4 Tail 6 Total 48

Table 31 illustrates an example of a SIG-A field that may be used in along format preamble in bandwidth modes of 2 MHz or higher for multiuser (MU) transmissions (e.g., for up to four users). The first eightfields of the SIG-A field (i.e., MU/SU bit, STBC, Reserved, Nsts, BW,GID, SGI, and Coding-I) may be in a first symbol of the SIG-A field andthe last seven fields of the SIG-A field (i.e., Coding-II, Reserved,Length, ACK Indication, Reserved, CRC, and Tail) may be in a secondsymbol of the SIG-A field. It will be noted that the order of the Nstsand BW fields may be reversed as compared to the SU SIG-A field shown inTable 30. This reversal may lead to improved peak to average power ratio(PAPR) for the MU SIG-A field shown in Table 31.

TABLE 32 SIG field for 1 MHz mode Field of SIG (1 MHz) Bits DescriptionNsts 2 Number of space time streams SGI 1 Short Guard Interval Coding 21^(st) bit for coding type (LDPC/BCC), 2^(nd) bit for LDPC Nsym ambig.STBC 1 Reserved 1 MCS 4 Aggregation Bit 1 Whether A-MPDUs are in useLength 9 Dual interpretation based on Agg. bit ACK Indication 2 00 =Ack; 01 = BA; 10 = No Ack; 11 = reserved Reserved 3 CRC 4 Tail 6 Total36

Table 32 illustrates an example of a SIG field that may be used in 1 MHztransmissions. In a particular embodiment, the SIG field of Table 32occupies six symbols (36 bits with 6 bits/symbol at 1 MHz bandwidth).

FIG. 6 shows a flow chart of an aspect of an exemplary method 600 ofgenerating and transmitting a data unit. The method 600 may be used togenerate any of the data units and SIGNAL units described above. Thedata units may be generated at either an AP or a STA and transmitted toanother device in the wireless network. Although the method 600 isdescribed below with respect to elements of the wireless device 202 a(FIG. 3), those having ordinary skill in the art will appreciate thatother components may be used to implement one or more of the stepsdescribed herein. Although steps may be described as occurring in acertain order, the steps can be reordered, steps can be omitted, and/oradditional steps can be added.

At 602, the processor 204 generates a SIGNAL unit 520. The SIGNAL unit520 includes at least an encoded PAID field. The PAID field has a valueindicating that a portion of the signal unit is to be decoded by one ormore devices which receive the signal unit, and the value of the PAIDfield indicates that the portion of the signal unit is not to be decodedby one or more other devices which receive the signal unit. In anembodiment, the modulator 302 may modulate a transmission that includesthe SIGNAL unit 520, and the transform module 304 may translate tonescorresponding to the transmission into the time domain. Advancing to604, the transmitter 210 transmits a data unit including the SIGNAL unitover a wireless channel.

FIG. 7 shows a flow chart of another aspect of an exemplary method 700of receiving and processing a data unit including a SIGNAL unit 520. Themethod 700 may be used to receive any of the data units described above.The packets may be received at either an AP or a STA from another devicein the wireless network. Although the method 700 is described below withrespect to elements of the wireless device 202 b (FIG. 4), those havingordinary skill in the art will appreciate that other components may beused to implement one or more of the steps described herein. Althoughsteps may be described as occurring in a certain order, the steps can bereordered, steps can be omitted, and/or additional steps can be added.

At 702, the receiver 212 receives a SIGNAL unit 520. The SIGNAL unit 520includes at least an encoded PAID field. For example, the SIGNAL unit520 can include one or more of the fields shown above in Tables 1-28.Advancing to 704, the processor 204 decodes the PAID field. Continuingto 706, the processor 204 determines whether the PAID field has a valueindicating that an undecoded portion of the SIGNAL unit 520 is to bedecoded. At 708, the processor 204 decodes the SIGNAL unit 520 if thevalue of the PAID field has a value indicating that the SIGNAL unit 520is to be decoded. At 710, the processor 204 defers for a time if thevalue of the PAID field does not have a value indicating that the SIGNALunit 520 is to be decoded.

In at least some embodiments discussed above, the SIGNAL units 520 arecoded using a convolutional code, and tail bits are included in theSIGNAL units 520. The tail bits may be all zeros, as in a “zero-tailcode,” and are used to return the encoder to the zero state, such thatthe decoding process at the receiver can be initiated from the zerostate. By adding the tail bits to the end of each SIGNAL unit 520, theencoder is returned to the zero state before every SIGNAL unit 520.Thus, each SIGNAL unit 520 may be encoded separately from every otherSIGNAL unit 520 by re-initialization of the encoder before every SIGNALunit 520. The independently encoded SIGNAL units 520 may also bemodulated independently. Further, both the start and end states of theencoder are known to a decoder used to decode the SIGNAL unit 520. Assuch, each SIGNAL unit 520 may be decoded and, in some cases,demodulated separately from each other SIGNAL unit 520.

In some embodiments, the SIGNAL unit 520 can be transmitted as a shortblock code. For example, any of the embodiments discussed herein may betransmitted as a short block code. Accordingly, in some embodiments, theSIGNAL unit 520 has no tail bits (referred to as “tail biting”). Forexample, SIGNAL unit 520 may be the same as any of the other embodimentsdiscussed herein except for having no tail bits. For example, any of theembodiments discussed with reference to Tables 1-28 may be transmittedas a short block code without the tail bits.

The SIGNAL unit 520 may be encoded as a linear block code or a shortblock code using, for example, an extended Hamming code, such as an (8,4, 4) rate ½ extended Hamming code. The SIGNAL unit 520 may be encodedas a short block code using, for example, an extended Golay code, suchas a (24, 12, 8) rate ½ extended Golay code. The SIGNAL unit 520 may beencoded as a short block code using, for example, a quadratic-residue(QR) code, such as a (48, 24, 12) rate ½ QR code. The SIGNAL unit 520may be encoded as a short block code using, for example, a tail bitingconvolution code (TBCC), such as a TBCC code discussed below.

When tail biting is used, no tail bits are included in the SIGNAL unit520. Rather, the last, e.g., “n” bits (where “n” is representative of apredetermined number of bits), of the SIGNAL unit 520 are used toinitialize the encoder, making the start and end states of the encoderidentical, but not necessarily zero. By using the last “n” bits of theSIGNAL unit 520 to initialize the encoder, each field or sub-field ofthe SIGNAL unit 520 may be encoded separately from every other field orsub-field by cyclically applying convolutional coding to each field orsub-field. The independently encoded fields or sub-fields may also bemodulated independently. With tail biting encoding, the decoder knowsthat the start and end states of the encoder are identical but does notknow what those states are. Thus, the decoder must be able to determinethe start and end states in order to decode the field or sub-field, forexample, by applying convolutional decoding on a repetition of thereceived field or sub-field. A decoder may be able to determine thestart and end states of the fields or sub-fields from informationprovided in the preamble. As such, each field or sub-field may bedecoded and, in some cases, demodulated separately from each other fieldor sub-field in the SIGNAL unit 520. When tail biting is used, a CRC mayalso be added to each field or sub-field, such that determination may bemade as to whether each field or sub-field has been decodedsuccessfully, independently of each other field or sub-field in theSIGNAL unit 520. The encoding process may result in a sequence of codesymbols for each field or sub-field that may be blocked together andmapped to a signal constellation to produce one or more modulationsymbols for each field or sub-field.

FIG. 8 shows a flow chart of an aspect of an exemplary method 800 ofgenerating and transmitting a data unit. The method 800 may be used togenerate any of the data units and SIGNAL units 520 described above. Thedata units may be generated at either the AP 104 or the STA 106 andtransmitted to another node in the wireless network. Although the method800 is described below with respect to elements of the wireless device202 a (FIG. 3), those having ordinary skill in the art will appreciatethat other components may be used to implement one or more of the stepsdescribed herein. Although steps may be described as occurring in acertain order, the steps can be reordered, steps can be omitted, and/oradditional steps can be added.

At 802, the processor 204 generates a SIGNAL unit 520. The SIGNAL unit520 includes at least a length field and one or more additional fields.For example, the SIGNAL unit 520 can include one or more of the fieldsshown above in Tables 1-28. A first field of the one or more additionalfields can include an exceptional value indicative of a zero-lengthpayload. As discussed above, an exceptional value can include a fieldvalue outside the normal bounds of operation. In an embodiment, themodulator 302 may modulate a transmission that includes the SIGNAL unit520, and the transform module 304 may translate tones corresponding tothe SIGNAL unit 520 into the time domain. At 804, the transmitter 210transmits a data unit including the SIGNAL unit 520 over a wirelesschannel.

FIG. 9 shows a flow chart of another aspect of an exemplary method 900of receiving and processing a data unit including a SIGNAL unit 520. Themethod 900 may be used to receive any of the data units described above.The packets may be received at either the AP 104 or the STA 106 fromanother node in the wireless network. Although the method 900 isdescribed below with respect to elements of the wireless device 202 b(FIG. 4), those having ordinary skill in the art will appreciate thatother components may be used to implement one or more of the stepsdescribed herein. Although steps may be described as occurring in acertain order, the steps can be reordered, steps can be omitted, and/oradditional steps can be added.

At 902, the receiver 212 receives a SIGNAL unit 520. The SIGNAL unit 520includes at least a length field and one or more additional fields. Forexample, the SIGNAL unit 520 can include one or more of the fields shownabove in Tables 1-28. Continuing to 904, the processor 204 determineswhether a first field of the one or more additional fields has anexceptional value indicative of a zero-length payload. As discussedabove, an exceptional value can include a field value outside the normalbounds of operation.

Advancing to 906, the processor 204 decodes the length field based onthe determined exceptional value. For example, the MCS field may includethe exceptional value of all-ones. The processor 204 may then decode thereserved bits and determine an alternative frame type. For example, theprocessor 204 may determine an ACK frame type. The processor 204 maythen decode the bits in the length field in relation to one or moreparameters of the ACK frame.

In a particular embodiment, a device may generate a SIG unit (e.g., theSIGNAL unit 520) that includes a length field and an aggregation field.For example, the length field may be nine bits long and the aggregationfield may be one bit long. Prior to, after, or during generation of theSIG unit, the device may determine whether or not to use aggregatedtransmission (e.g., A-MPDUs). In a particular embodiment, aggregatedtransmission may be mandatory for frame sizes greater than or equal to512 bytes in size, but may be optional for frame sizes less than 512bytes. In response to determining to use aggregated transmission, thedevice may set the aggregation field to a first value (e.g., “1”) andmay set the length field to a number of symbols. In response todetermining not to use aggregated transmission, the device may set theaggregation field to a second value (e.g., “0”) and may set the lengthfield to a number of bytes. The device may transmit the SIG unit via awireless network (a sub-1 GHz network in compliance with an IEEE802.11ah protocol). The SIG unit may be included in a preamble of aframe, such as a single user (SU) or multi user (MU) frame.

In a particular embodiment, a device may receive a SIG unit (e.g., theSIGNAL unit 520) that includes length field and an aggregation field.The device may interpret the length field as a number of symbols inresponse to determining that the aggregation field has a first value(e.g., “1”). The device may interpret the length field as a number ofbytes in response to determining that the aggregation field has secondvalue (e.g., “1”).

In another particular embodiment, the device may initially determinewhether the frame including the SIG unit is associated with 1 MHzbandwidth. If the frame is associated with the 1 MHz bandwidth, thedevice may interpret the length field as a number of bytes or a numberof symbols based on the value of the aggregation field, as describedabove. However, if the frame is not associated with the 1 MHz bandwidth,the device may determine whether the frame has a short format preambleor a long format preamble (e.g., by checking a rotation of the SIGunit). If the frame has the short format preamble, the device mayinterpret the length field as a number of bytes or a number of symbolsbased on the value of the aggregation field, as described above.Conversely, if the frame has the long format preamble, the device maydetermine whether the frame is a SU frame or a MU frame (e.g., bychecking an SU/MU field). If the frame is a SU frame, the device mayinterpret the length field as a number of bytes or a number of symbolsbased on the value of the aggregation field, as described above. If theframe is a MU frame, the device may automatically interpret the lengthfield as a number of symbols (e.g., because a wireless protocol orstandard, such as IEEE 802.11ah, may mandate that the length of a MUframe having a long format preamble be represented as a number ofsymbols).

FIG. 10 is a functional block diagram of another exemplary wirelessdevice 1000 that may be employed in accordance with the presentdisclosure. The device 1000 includes a generating module 1002 forgenerating a data unit for wireless transmission. The generating module1002 may be configured to perform one or more of the functions discussedabove with respect to block 602 of FIG. 6 and/or block 802 of FIG. 8.The generating module 1002 may correspond to one or more of theprocessor 204 and the DSP 220. The device 1000 further includes atransmitting module 1004 for wirelessly transmitting the data unit. Thetransmitting module 1004 may be configured to perform one or more of thefunctions discussed above with respect to block 604 of FIG. 6 and/orblock 804 of FIG. 8. The transmitting module 1004 may correspond to thetransmitter 210. In a particular embodiment, the data unit may include aSIGNAL unit (e.g., the SIGNAL unit 520), where a length field of theSIGNAL unit is interpreted based on a value of an aggregation fieldand/or where a particular field of the SIGNAL unit has a valueindicating a zero-length payload.

FIG. 11 is a functional block diagram of yet another exemplary wirelessdevice 1100 that may be employed in accordance with the presentdisclosure. The device 1100 includes a receiving module 1102 forwirelessly receiving a data unit. The receiving module 1102 may beconfigured to perform one or more of the functions discussed above withrespect to block 702 of FIG. 7 and/or block 902 of FIG. 9. The receivingmodule 1102 may correspond to the receiver 212, and may include theamplifier 401.

The device 1100 further includes a determining module 1104 fordetermining various characteristics of the data unit. For example, thedetermining module 1104 may determine whether a first field of the oneor more additional fields has an exceptional value indicative of azero-length payload. As discussed above, an exceptional value caninclude a field value outside the normal bounds of operation. As anotherexample, the determining module may determine a PAID field has a valueindicating that an undecoded portion of a SIG unit is to be decoded. Thedetermining module 1104 may be configured to perform one or more of thefunctions discussed above with respect to block 904 of FIG. 9 and/orblock 706 of FIG. 7. The determining module 1104 may correspond to oneor more of the processor 204, the signal detector 218, and the DSP 220.

The device 1100 further includes a decoding module 1106 for decodingdata. For example, the decoding module 1106 may decode the length fieldbased on the determined exceptional value. The decoding module 1106 mayalso decode a PAID field and a SIG unit if a value of the PAID fieldindicates that the SIG unit is to be decoded. The decoding module 1106may defer for a time if the value of the PAID field indicates that theSIG unit is not to be decoded. The decoding module 1106 may beconfigured to perform one or more of the functions discussed above withrespect to block 704 of FIG. 7, block 708 of FIG. 7, block 710 of FIG.7, and/or block 906 of FIG. 9. The decoding module 1106 may correspondto one or more of the processor 204, the signal detector 218, and theDSP 220, and may include the channel estimator and equalizer 405.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like. Further, a “channel width” as used herein may encompass ormay also be referred to as a bandwidth in certain aspects.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: only a;only b; only c; a and b; a and c; b and c; and a, b, and c.

The various operations of methods described above may be performed byany suitable means capable of performing the operations, such as varioushardware and/or software component(s), circuits, and/or module(s).Generally, any operations illustrated in the Figures may be performed bycorresponding functional means capable of performing the operations.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array signal (FPGA) or other programmable logic device(PLD), discrete gate or transistor logic, discrete hardware componentsor any combination thereof designed to perform the functions describedherein. A general purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

In one or more aspects, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over as oneor more instructions or code on a computer-readable medium.Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage media may be anyavailable media that can be accessed by a computer. By way of example,and not limitation, such computer-readable media can include RAM, ROM,EEPROM, CD-ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other medium that can be used tocarry or store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Thus, in some aspects computer-readable medium may includenon-transitory computer-readable medium (e.g., tangible media). Inaddition, in some aspects computer-readable medium may includetransitory computer-readable medium (e.g., a signal). Combinations ofthe above should also be included within the scope of computer-readablemedia.

The methods disclosed herein include one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The functions described may be implemented in hardware, software,firmware or any combination thereof. If implemented in software, thefunctions may be stored as one or more instructions on acomputer-readable medium. A storage media may be any available mediathat can be accessed by a computer. By way of example, and notlimitation, such computer-readable media can include RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers.

Thus, certain aspects may include a computer program product forperforming the operations presented herein. For example, such a computerprogram product may include a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For certain aspects, the computer program product may includepackaging material.

Software or instructions may also be transmitted over a transmissionmedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition oftransmission medium.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

While the foregoing is directed to aspects of the present disclosure,other and further aspects of the disclosure may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A method comprising: generating, at a secondwireless device, a signal (SIG) unit to be transmitted to a firstwireless device, wherein the SIG unit comprises a length field and anaggregation field; in response to determining to use aggregatedtransmission to the first wireless device, setting the aggregation fieldto a first value and setting the length field to a number of symbols;and in response to determining not to use the aggregated transmission tothe first wireless device, setting the aggregation field to a secondvalue and setting the length field to a number of bytes.
 2. The methodof claim 1, further comprising transmitting the SIG unit to the firstwireless device via a sub-1 gigahertz (GHz) wireless network.
 3. Themethod of claim 2, wherein the sub-1 GHz wireless network operates inaccordance with an Institute of Electrical and Electronics Engineers(IEEE) 802.11ah protocol.
 4. The method of claim 1, wherein the lengthfield is a 9-bit field.
 5. The method of claim 1, wherein theaggregation field is a 1-bit field.
 6. The method of claim 1, whereinthe SIG unit is included in a preamble of a packet.
 7. The method ofclaim 1, wherein the SIG unit further comprises a partial associationidentifier (PAID) field.
 8. The method of claim 7, wherein the PAIDfield is a 9-bit field.
 9. The method of claim 1, wherein the aggregatedtransmission comprises one or more aggregated media access control (MAC)protocol data units (A-MPDUs).
 10. The method of claim 1, furthercomprising determining to use the aggregated transmission in response todetermining that the SIG unit is part of a multi user (MU) frame. 11.The method of claim 1, further comprising determining to use theaggregated transmission in response to determining that the SIG unit ispart of a frame that is longer than 511 bytes.
 12. The method of claim1, further comprising transmitting the SIG unit to the first wirelessdevice via a sub-1 gigahertz (GHz) wireless network, wherein the lengthfield is a 9-bit field and the aggregation field is a 1-bit field,wherein the SIG unit corresponds to a short format preamble and abandwidth mode greater than or equal to 2 megahertz (MHz), and whereinthe SIG unit further comprises: a 1-bit first reserved field; a 1-bitspace-time block code (STBC) field; a 1-bit second reserved field; a2-bit bandwidth field; a 2-bit number of space time streams field; a9-bit partial association identifier field; a 1-bit short guard interval(SGI) field; a 2-bit coding field; a 4-bit modulation and coding scheme(MCS) field; a 1-bit smoothing field; a 2-bit acknowledgement (ACK)indication field; a 4-bit cyclic redundancy check (CRC) field; and a6-bit tail field.
 13. The method of claim 12, wherein the SIG unitfurther comprises two orthogonal frequency-division multiplexing (OFDM)symbols, wherein the SIG unit is encoded at a rate of one-half, andwherein the SIG unit corresponds to a binary phase-shift keying (BPSK)constellation.
 14. The method of claim 1, further comprisingtransmitting the SIG unit to the first wireless device via a sub-1gigahertz (GHz) wireless network, wherein the length field is a 9-bitfield and the aggregation field is a 1-bit field, wherein the SIG unitcorresponds to a long format single user (SU) preamble and a bandwidthmode greater than or equal to 2 megahertz (MHz), and wherein the SIGunit comprises: a 1-bit multi user (MU)/SU field; a 1-bit space-timeblock code (STBC) field; a 1-bit reserved field; a 2-bit bandwidthfield; a 2-bit number of space time streams field; a 9-bit partialassociation identifier field; a 1-bit short guard interval (SGI) field;a 2-bit coding field; a 4-bit modulation and coding scheme (MCS) field;a 1-bit beam-change indication field; a 2-bit acknowledgement (ACK)indication field; a 4-bit cyclic redundancy check (CRC) field; and a6-bit tail field.
 15. The method of claim 14, wherein the SIG unitfurther comprises two orthogonal frequency-division multiplexing (OFDM)symbols, wherein the SIG unit is encoded at a rate of one-half, andwherein the SIG unit corresponds to a binary phase-shift keying (BPSK)constellation.
 16. The method of claim 1, further comprisingtransmitting the SIG unit to the first wireless device via a sub-1gigahertz (GHz) wireless network, wherein the length field is a 9-bitfield and the aggregation field is a 1-bit field, wherein the SIG unitcorresponds to a 1 megahertz (MHz) bandwidth mode, and wherein the SIGunit further comprises: a 2-bit number of space time streams field; a1-bit short guard interval (SGI) field; a 2-bit coding field; a 1-bitspace-time block code (STBC) field; a 1-bit first reserved field; a4-bit modulation and coding scheme (MCS) field; a 2-bit acknowledgement(ACK) indication field; a 4-bit cyclic redundancy check (CRC) field; anda 6-bit tail field.
 17. The method of claim 16, wherein the SIG unitfurther comprises six orthogonal frequency-division multiplexing (OFDM)symbols, wherein the SIG unit is encoded at a rate of one-half, andwherein the SIG unit corresponds to a binary phase-shift keying (BPSK)constellation.
 18. An apparatus comprising: a processor configured to:generate a signal (SIG) unit, wherein the SIG unit comprises a lengthfield and an aggregation field; in response to determining to useaggregated transmission, set the aggregation field to a first value andset the length field to a number of symbols; and in response todetermining not to use the aggregated transmission, set the aggregationfield to a second value and set the length field to a number of bytes;and a transmitter configured to transmit the SIG unit.
 19. The apparatusof claim 18, wherein the processor is further configured to determine touse the aggregated transmission in response to determining that the SIGunit is part of a multi user (MU) frame, in response to determining thatthe SIG unit is part of a frame that is longer than 511 bytes, or anycombination thereof.
 20. An apparatus comprising: means for generating asignal (SIG) unit that comprises a length field and an aggregationfield; and means for transmitting the SIG unit to a wireless device,wherein, in response to determining to use aggregated transmission tothe wireless device, the means for generating sets the aggregation fieldto a first value and sets the length field to a number of symbols, andwherein, in response to determining not to use the aggregatedtransmission to the wireless device, the means for generating sets theaggregation field to a second value and sets the length field to anumber of bytes.
 21. The apparatus of claim 20, wherein the means forgenerating is configured to determine to use the aggregated transmissionin response to determining that the SIG unit is part of a multi user(MU) frame, in response to determining that the SIG unit is part of aframe that is longer than 511 bytes, or any combination thereof.
 22. Anon-transitory computer-readable medium comprising instructions that,when executed by a computer, cause the computer to: generate a signal(SIG) unit to be transmitted to a wireless device, wherein the SIG unitcomprises a length field and an aggregation field; in response todetermining to use aggregated transmission to the wireless device, setthe aggregation field to a first value and set the length field to anumber of symbols; and in response to determining not to use theaggregated transmission to the wireless device, set the aggregationfield to a second value and set the length field to a number of bytes.23. The non-transitory computer-readable medium of claim 22, furthercomprising instructions that, when executed by the computer, cause thecomputer to determine to use the aggregated transmission in response todetermining that the SIG unit is part of a multi user (MU) frame, inresponse to determining that the SIG unit is part of a frame that islonger than 511 bytes, or any combination thereof.